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Malignant Fibrous Histiocytoma

(Undifferentiated Pleomorphic Sarcoma)

An ESUN Article by Peter J. Buecker, MD; Mark Gebhardt, MD and Kristy Weber, MD
Also available in Japanese and Spanish

What is Malignant Fibrous Histiocytoma?

Figure 1

Figure 1: A histologic specimen showing a classic storiform...

Malignant fibrous histiocytoma (MFH), a type of sarcoma, is a malignant neoplasm of uncertain origin that arises both in soft tissue and bone. It was first introduced in 1961 by Kauffman and Stout (Ref. 22) and controversy has plagued it since. They described MFH as a tumor rich in histiocytes with a storiform growth pattern. By 1977, MFH was considered the most common soft tissue sarcoma of adult life. Despite the frequency of diagnosis, MFH has remained an enigma. No true cell of origin has ever been identified. In 2002, the World Health Organization (WHO) declassified MFH as a formal diagnostic entity and renamed it as an undifferentiated pleomorphic sarcoma not otherwise specified, NOS (Ref. 4). This new terminology has been supported by a compelling body of evidence over the last decade to suggest that MFH represents a final common pathway in tumors that undergo progression towards undifferentiation (Refs. 5, 12, 15, and 19). While it remains unclear how to most accurately organize these tumors, the term malignant fibrous histiocytoma represents the diagnosis for thousands of patients and is still commonly used by both patients and physicians. This review will describe soft tissue tumors once diagnosed as MFH.

Figure 2

Figure 2: A histologic example of myxoid type MFH...

MFH manifests a broad range of histologic appearances with four sub-types described (Ref. 3):

  1. Storiform-pleomorphic
  2. Myxoid
  3. Giant cell
  4. Inflammatory

Of these, the storiform-pleomorphic is the most common type, accounting for up to 70% of most cases, see Figure 1. The myxoid variant is the second most common accounting for approximately 20% of cases, see Figure 2.

Unlike the other sub-types of MFH, the myxoid form tends to be less aggressive and as a result is associated with a better prognosis. Giant cell and inflammatory types are rare. Inflammatory MFH tends to occur in the retroperitoneum.

The myxoid subtype must contain at least 50% myxoid areas by definition. Occasionally an entire nodule of tumor can have a myxoid appearance causing diagnostic confusion including less aggressive entities such as myxoma or nodular fasciitis. Most myxoid variants of MFH behave as low grade neoplasms and thus pursue a less aggressive course.

How Does Malignant Fibrous Histiocytoma Present?

As with all sarcomas of soft tissue and bone, MFH is rare, with just a few thousand cases diagnosed each year.

MFH of soft tissue typically presents in a patient that is approximately 50 to 70 years of age though it can appear at any age. MFH is very rare in persons less than 20 years old.

There is a slight male predominance. Soft tissue MFH can arise in any part of the body but most commonly in the lower extremity, especially the thigh. Other common locations include the upper extremity and retroperitoneum. Patients often complain of a mass or lump that has arisen over a short period of time ranging from weeks to months. It is not uncommon for patients to report trauma to the affected area. For example, patients will state that they "ran into the corner of a table" and have had a thigh lump since. Trauma as far as we know does not cause MFH but rather the incident draws attention to the extremity. The mass does not usually cause any pain unless it is compressing a nearby nerve. Symptoms such as weight loss and fatigue are not typical but can present in patients with advanced disease. Retroperitoneal tumors can become quite large before they are detected as patients do not feel a mass per se but rather associated constitutional symptoms such as anorexia or increased abdominal pressure.

Because MFH is extremely rare in children, other diagnostic possibilities must be exhausted before accepting it as a diagnosis in the pediatric population.

Figure 3

Figure 3: Clinical photograph of an MFH of the proximal lateral thigh...

"I feel a lump. Now what?"

Not all lumps and bumps are cancerous and in fact, most are not. Nonetheless, all masses should be brought to the attention of a physician. Your doctor will likely ask a series of questions regarding the mass such as "How long has the mass been present?" and "Is it enlarging? If so, over what period of time?" She or he will then perform a thorough physical examination assessing the size and firmness of the mass, examining other parts of the affected extremity, and searching for enlarged lymph nodes.

Figure 4

Figure 4: Clinical picture of MFH in the hand...

Often an x-ray is obtained as the first imaging test. Usually this is followed with an MRI. MRI is the most useful test to image soft tissue tumors as it provides very valuable information about the mass such as the size, location, and proximity to neurovascular structures. It is important to note that the diagnosis of a cancerous tumor cannot be made by MRI alone. For patients that are unable to undergo MRI because of metallic implants such as pacemakers, a CT scan may be obtained.

After analyzing all of the information that has been gathered, if the mass remains suspicious for sarcoma the patient will likely be referred to a physician who specializes in sarcoma. The specialist, usually an orthopaedic oncologist or general surgical oncologist, will then likely perform additional tests and arrange for a biopsy.

Figure 5

Figure 5a and 5b: Images of an MFH in the thigh...

When the diagnosis of sarcoma is suspected, it is important to determine if a tumor is isolated (localized) or has spread (metastatic). When soft tissue sarcomas spread, they most commonly metastasize to the lungs. As such, a CT scan of the chest is routinely obtained to determine the presence or absence of metastatic disease. While sarcomas including MFH can spread to other sites such as lymph nodes and bones, it is fairly uncommon. The role of tests such as bone scan and PET scan is not totally clear (Refs. 20, 23, and 30). There is considerable variability among physicians as to whether these additional studies are useful.

Metastasis: The vast majority of metastatic disease from sarcomas including MFH present as pulmonary disease (90%). Involvement of extra-pulmonary sites is uncommon: lymph nodes (10%), bone (8%), liver (1%).

PET scans exploit the high metabolic activity of cancer cells. The technique utilizes the radiolabeled glucose analog (Ref. 18) fluoro-2-deoxy-D-glucose which is metabolized at higher rates by the tumor cells. The uptake of the FDG is expressed as maximum standard uptake value (SUV). While it is a very sensitive test, it is not specific for sarcoma. Several investigations have attempted to define the role of PET scanning in soft tissue sarcomas (refs. 13, 33, and 34). As our understanding of this new technology develops, its diagnostic and staging capabilities will become more refined. For now, the role and cost-effectiveness of PET scanning have yet to be clearly defined.

Biopsy

Figure 6

Figure 6: Needle biopsy of an MFH in the thigh...

A biopsy is a procedure in which diagnostic tissue is obtained. Biopsies can be performed by different methods. A needle biopsy involves inserting a small needle into the tumor to obtain a specimen (Refs. 17 and 45). Needle biopsies, see Figure 6, can often be performed in the physician’s office. If the tumor is in a location that is difficult to feel or there are structures near the tumor that could be damaged, then a CT-guided needle biopsy might be arranged.

An open biopsy is a surgical procedure that is usually performed in the operating room under sedation or anesthesia. With incisional biopsies, just a small part of the tumor is removed for analysis. With excisional biopsies, the entire mass is removed. Excisional biopsies are usually reserved for small tumors (less than 3 cm).

Figure 7

Figure 7: Limb sparing incision in the upper extremity for a sarcoma of the...

The decision to remove part of the mass or the entire mass at the time of biopsy is extremely critical. The importance of having a sarcoma specialist either perform the actual biopsy or guide the treating surgeon in planning a biopsy cannot be overstated.

The biopsy is often the first step to a successful limb-sparing procedure. The location of the biopsy incision and technical aspects of obtaining tissue can have a major impact on subsequent operations (Ref. 28).

The tissue obtained from the biopsy is evaluated by a pathologist. The pathologist uses a number of diagnostic tools including light microscopy, immunohistochemistry, electron microscopy, and molecular studies to make the diagnosis. In addition to making a diagnosis, the pathologist also provides an important piece of information called the grade. The grade refers to a tumor’s appearance under the microscope and is a reflection of a tumor’s aggressiveness. High grade tumors behave more aggressively meaning they have a higher tendency to recur and spread. Low grade tumors are less aggressive and have a lower tendency to recur and spread. The grade is not a guarantee of a tumor’s behavior but rather is one of the factors that helps the treatment team make recommendations.

Several cytogenetic abnormalities have been described for STS including MFH. More than 80% of MFH tumors display mutations affecting 1q31, 9q31,5p14, and 7q32. Abnormalities at 3p12, 11p11, and 19p13have also been described. In a multivariate analysis of tumor grade and size, gains at 7q32 predicted a worse survival (Ref. 24).

Staging

Once all of the imaging studies and biopsy have been performed, the stage of disease can be assigned. The most commonly used staging system is the AJCC (American Joint Commission on Cancer) system for soft tissue sarcoma, see Table 1 (Ref. 1). Patients often inquire about the stage of their disease. It must be kept in mind that stage is not a guarantee of a tumor’s behavior. Staging merely provides guidelines for the treatment team on how best to manage a given tumor to optimize clinical outcome.

Table 1: The American Joint Committee on Cancer (AJCC)  Staging System for Soft Tissue Sarcoma, 6th Edition
Stage Size Depth Grade Metastases
I Any Any Low No
II < 5cm, any depth OR > 5cm Superficial High No
III > 5cm Deep High No
IV Any Any Any Yes

*Depth is termed superficial (above the deep fascia) or deep (deep to the deep fascia). Retroperitoneal tumors are considered deep.

"I have MFH. What are the next steps?"

Once the diagnosis of MFH has been confirmed, an individual treatment plan is made for each patient. Sarcoma treatment requires a multimodality approach and hence a team of physicians will participate in a patient’s care. There are essentially three main types of treatment that will need to be coordinated to treat the MFH:

  1. Surgery
  2. Radiation
  3. Chemotherapy

Surgery

Surgery is the cornerstone of treatment for all soft tissue sarcomas. The goal of surgery is to eradicate all disease in the affected area. For extremity sarcomas, surgical options fall into two categories: limb-sparing and amputation. Historically, soft tissue sarcomas were treated with amputation. As our understanding of sarcoma has evolved, so has the treatment. Several studies have demonstrated no difference in patient survival with amputation versus limb-salvage (Refs. 46 and 47). In a randomized clinical trial run by the National Cancer Institute (ref. 40), there was no difference in overall survival for patients with soft tissue sarcoma that had amputation (70%) versus those that had amputation (71%). Currently at least 90% of tumors are now removed using limb-sparing surgery meaning that the tumor is removed while saving the extremity. Limb sparing surgery should only be performed if the surgeon is confident that the tumor can be completely removed and that the remaining extremity provides reasonable function. Obviously balancing oncologic and functional outcomes is a very complex and subjective undertaking. It is very important that the patient and treating surgeon discuss the expectations of all options preoperatively. Reconstruction following tumor resection is sometimes necessary depending on the size of the tumor and what structures need to be sacrificed. For example, a bone or joint may need to be reconstructed or soft tissue flaps may be needed for wound coverage.

Figure 8

Figure 8: Intra-operative photograph of an MFH of the scapula...

Once a tumor has been removed, the pathologist analyzes the entire specimen to confirm the tumor’s grade and margins. The term margin refers to the outermost edges of a resection specimen. A negative marginindicates that there are no tumor cells on the periphery of the tumor implying that a complete resection was achieved. A positive margin means that tumor cells were found on the periphery of the resection specimen which implies there is likely residual microscopic disease. Obviously one hopes to achieve negative margins at the time of surgery. Unfortunately it is not always possible to accomplish this. Surgical procedures for sarcoma are classified as outlined in Table 2. When possible, wide and radical procedures are attempted in order to obtain negative margins.

Table 2: Classification of surgical resections for the treatment of sarcoma
Intralesional Partial removal of the tumor
Marginal Through the reactive zone; may leave residual microscopic disease
Wide Entire tumor removed with a cuff of normal tissue
Radical Entire compartment containing the tumor removed

Radiation

Radiation therapy is administered by a radiation oncologist. The purpose of radiation is to improve local tumor control by killing residual microscopic disease. Radiation has been clearly shown to improve the incidence of local recurrence and has become an integral part of the treatment for MFH (Refs. 6 and 27). Typical radiation doses vary from 45 Gy to 65 Gy.

In a prospective randomized trial from NCI, 91 patients with high grade tumors were randomized to surgery alone or surgery with post-operative external beam radiation therapy, XRT (Ref. 48). Patients in the surgery alone group experience 20% local recurrence rates compared to 0% for the surgery plus XRT group. For both groups, there was no difference in overall survival. In general, patients treated with adequate limb-sparing surgery supplemented with radiation have a likelihood of experiencing over 85% local control.

There are several different ways to administer radiation. The most commonly used form of radiation is external beam radiation which can be given pre-operatively, intra-operatively, post-operatively, or in some combination. Each has advantages and disadvantages, see Table 3. For tumors that are in contact with major nerves and blood vessels, pre-operative radiation can potentially shrink the tumor, making limb-sparing surgery possible or easier. The main disadvantage to pre-operative radiation is its association with post-operative wound complications (Refs. 10 and 35). Post-operative radiation is probably the most commonly used modality. Typically pre- and post-operative radiation is administered over a 5 week period. Intra-operative has the advantage of delivering a large dose of radiation directly to an area of concern while sparing nearby organs such as the bowel or bladder. It is particularly useful for treating large retroperitoneal sarcomas in which it is difficult to obtain local tumor control (Ref. 43).

Table 3: The advantages and disadvantages 
of the timing of radiation therapy
Delivery Method Advantages Disadvantages
Pre-operative
  1. potentially shrinks tumor
  2. smaller volume required
  1. increase in wound complications 
  2. delay in definitive surgery
Intra-operative
  1. can concentrate very high doses to close margins 
  2. minimal injury to normal tissue
  1. requires a special operating room with exposure to O.R. staff
  2. wound complications
Postoperative
  1. fewer wound complications 
  2. immediate surgery
  1. larger volume required secondary to operative contamination

Another means of administering radiation is a technique called brachytherapy. After the surgeon has removed the tumor, a radiation oncologist then places empty catheters in the operative bed. Once the wound is starting to heal (approximately 5 days after surgery), the catheters are filled with radioactive material which sits in the surgical bed for 5 days. This allows for high doses of radiation over a short period of time obviating the need to travel daily for radiation treatments over several weeks.

In a prospective randomized trial conducted at the Memorial Sloan-Kettering Cancer Center, 164 patients with extremity or superficial axial sarcomas were randomized to surgery alone versus surgery plus brachytherapy (Ref. 38). For patients with high grade tumors, the 5-year local control rate was 89% in the brachytherapy group, compared to 66% in the surgery only group. There was no difference in overall survival between the groups. A retrospective review from the same institution examined small (<5cm) high grade sarcomas treated with brachytherapy (Ref. 37). There was no advantage in local control or overall survival for this subgroup of patients.

Figure 9

Figure 9: Brachytherapy catheters traversing the operative field...

Unfortunately radiation does have well known side effects. Problems with wound healing have already been described above. Problems including scarring of the tissue resulting in firm stiff muscles, as well as skin discoloration, have also been well described. The most serious complication arising from radiation is the development of a second cancer within the radiated field (Refs. 8, 29, and 32). This is called a post-radiation or radiation-induced sarcoma. Radiation-induced sarcomas are rare and occur in less than 5% of long-term survivors.

Chemotherapy

The role of chemotherapy in the treatment of MFH is not entirely clear. Several clinical trials incorporating the chemotherapy drug doxorubicin have shown trends in improved event-free survival without a major impact on overall survival. The results of a large meta-analysis which included almost 1,600 soft tissue sarcoma patients concluded that the addition of chemotherapy improved overall survival by less than 10% (Ref. 2). Results were better in patients with extremity tumors than in patients with axial or retroperitoneal tumors. More recently, clinical trials incorporating ifosfamide and doxorubicin have demonstrated an improvement in disease-free survival (Refs. 26 and 36). One of the major limitations of chemotherapy is the associated toxicities with the doses necessary to have a significant impact on disease-specific survival. The addition of supportive drugs such as hematopoietic growth factors has allowed for higher doses and trends in improved survival are being observed.

Unfortunately, the interpretation of these and other chemotherapy trials results has varied so much that it has become difficult for patients to decipher the information in order to make decisions regarding chemotherapy as part of their treatment. The decision to incorporate chemotherapy in the treatment of MFH must be made with the guidance of a medical oncologist. Chemotherapy probably should be given to patients who already have metastatic disease or who are at the highest risk for developing metastatic disease. Most often, chemotherapy will likely be administered in the setting of a clinical trial.

Prognosis and Outcome

Prognostic factors that are known to correlate with survival in patients with MFH include tumor grade, depth, size, metastatic status, patient’s age, and histologic subtype (Refs. 11, 16, and 39). Favorable prognostic factors include age less than 60 years old, tumor size less than 5 cm, superficial location, low grade, the absence of metastatic disease, and a myxoid subtype. Older patients with large (> 5cm), deeply seated, high grade tumors do not have as favorable an outcome. For example, patients with a small low grade tumor are likely to achieve complete cure. For patients with large, deep, high grade tumors (Stage III), the 5 year survival estimates range from 34 to 70% (Refs. 25, 42, and 49).

Sarcoma Nomogram

On the basis of a prospectively followed cohort of adult patients with primary soft tissue sarcoma (STS) who were treated at Memorial Sloan-Kettering Cancer Center, a nomogram for predicting sarcoma-specific mortality at 12 years was developed (Ref. 21). Nomogram predictor variables included age at diagnosis, tumor size (< or = 5, 5 to 10, or > 10 cm), histologic grade (high or low), histologic subtype (fibrosarcoma, leiomyosarcoma, liposarcoma, malignant fibrous histiocytoma, malignant peripheral nerve tumor, synovial, or other), depth (superficial or deep), and site (upper extremity, lower extremity, visceral, thoracic or trunk, retrointraabdominal, or head or neck. The accuracy of the nomogram has been validated by both internal and external standards (Ref. 14). The tool is meant to be used in adult patients who are less than 6 months from their index surgical procedure and are without evidence of metastatic disease. The sarcoma nomogram may be useful for patient counseling, follow-up scheduling, and clinical trial eligibility determination. It is available to health care professionals by clicking here.

Local recurrence (LR), recurrence of the tumor in the same location, will occur in approximately 20-30% of all patients with soft tissue sarcomas (Refs. 25, 42, and 49). LR is lowest in extremity sarcomas and highest in retroperitoneal and head and neck sarcomas. This distribution is directly related to the ability to completely resect a tumor at the time of surgery. Higher LR rates are observed in the setting of positive surgical margins, which are more difficult to achieve in anatomic locations outside of the extremity (Ref. 18). Whether local control has an impact on overall survival is unclear and remains controversial. Several well designed investigations have been reported that support both sides of the argument.

It is very important for patients to understand that the data on outcomes and survival is derived from mostly heterogeneous, retrospective analyses that lack strict inclusion criteria. The survival statistics that are quoted are most useful to the treating physician to guide therapy and probably of limited value for an individual patient.

Table 4: Clinical Outcome of Malignant Fibrous Histiocytoma
from Large Cancer Centers
Center # of Patients Local Recurrence (%) Metastasis (%) 5-Year Survival
Memorial Sloan-Kettering Cancer Center
230
19
35
65
MD Anderson Cancer Center
271
21
31
68
French Federation of Cancer Centers
216
31
33
70

Follow-up Care and Surveillance

Probably about 1/3 of patients with extremity MFH and closer to ½ of patients with retroperitoneal MFH will experience recurrence either in the primary site (local recurrence) or at a distant site (distant recurrence or metastasis). Most recurrences usually develop in the first 2 years following treatment but may occur at any time during a patient’s lifetime. The frequency and length of follow-up vary according to the number of risk factors an individual has for developing a recurrence. On average patients are followed for approximately 10 years. Patients with large or high grade tumors will likely be evaluated every few months initially where as patients with low grade or small tumors will probably be seen annually. A follow-up exam consists of a physical examination and a chest evaluation in the form of an x-ray or CT-scan. Depending on the circumstances, an MRI of the primary site may be obtained.

If a recurrence is detected, the treatment team collaborates again to determine the roles of surgery, radiation, and chemotherapy. Most local recurrences can be effectively treated with additional surgery. For recurrent local disease that is resectable, approximately 2/3 of patients experience long term survival (Refs. 31 and 44). If no prior radiation was administered, the affected area should receive radiation for the recurrence. Metastatic disease represents the most serious type of recurrence and most commonly occurs in the lungs. Individual treatment plans vary significantly depending on a host of patient and disease factors as well as the limitations imposed by previous treatments. For patients that have isolated resectable pulmonary metastases, it is possible to achieve extended survival in approximately 20% to 50% of patients (Refs. 7, 9, and 41). Chemotherapy is often incorporated into the treatment of patients with distant recurrence. Unfortunately, patients with unresectable recurrent disease have a uniformly poor prognosis.

Summary

  • MFH is a curable disease.
  • The term "Malignant Fibrous Histiocytoma" has been changed by the WHO to Undifferentiated Pleomorphic Sarcoma Not Otherwise Specified.
  • The mainstays of treatment for MFH are complete surgical excision most often supplemented with adjuvant radiation therapy.
  • Chemotherapy is reserved for patients at the highest risk of disease recurrence or patients that already have recurrence.
  • Patients with recurrent MFH can still be cured.
  • Favorable prognostic factors that correspond to superior survival include small tumor size, low grade, extremity location, superficial location, and localized disease.

Last revision and medical review: 4/2005

By Carol D. Morris, MD, MS
Attending Orthopaedic Surgeon
Memorial Sloan-Kettering Cancer Center
Assistant Professor of Orthopaedic Surgery
Weill Medical College
Cornell University
New York, NY

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40. Rosenberg, S. A. et al.: The treatment of soft-tissue sarcomas of the extremities: prospective randomized evaluations of (1) limb-sparing surgery plus radiation therapy compared with amputation and (2) the role of adjuvant chemotherapy. Ann Surg, 196(3): 305-15, 1982.

41. Roth, J. A.; Putnam, J. B., Jr.; Wesley, M. N.; and Rosenberg, S. A.: Differing determinants of prognosis following resection of pulmonary metastases from osteogenic and soft tissue sarcoma patients. Cancer, 55(6): 1361-6, 1985.

42. Salo, J. C.; Lewis, J. J.; Woodruff, J. M.; Leung, D. H.; and Brennan, M. F.: Malignant fibrous histiocytoma of the extremity. Cancer, 85(8): 1765-72, 1999.

43. Sindelar, W. F.; Kinsella, T. J.; Chen, P. W.; DeLaney, T. F.; Tepper, J. E.; Rosenberg, S. A.; and Glatstein, E.: Intraoperative radiotherapy in retroperitoneal sarcomas. Final results of a prospective, randomized, clinical trial. Arch Surg, 128(4): 402-10, 1993.

44. Singer, S.; Antman, K.; Corson, J. M.; and Eberlein, T. J.: Long-term salvageability for patients with locally recurrent soft-tissue sarcomas. Arch Surg, 127(5): 548-53; discussion 553-4, 1992.

45. Skrzynski, M. C.; Biermann, J. S.; Montag, A.; and Simon, M. A.: Diagnostic accuracy and charge-savings of outpatient core needle biopsy compared with open biopsy of musculoskeletal tumors. J Bone Joint Surg Am, 78(5): 644-9, 1996.

46. Williard, W. C.; Collin, C.; Casper, E. S.; Hajdu, S. I.; and Brennan, M. F.: The changing role of amputation for soft tissue sarcoma of the extremity in adults. Surg Gynecol Obstet, 175(5): 389-96, 1992.

47. Williard, W. C.; Hajdu, S. I.; Casper, E. S.; and Brennan, M. F.: Comparison of amputation with limb-sparing operations for adult soft tissue sarcoma of the extremity. Ann Surg, 215(3): 269-75, 1992.

48. Yang, J. C. et al.: Randomized prospective study of the benefit of adjuvant radiation therapy in the treatment of soft tissue sarcomas of the extremity. J Clin Oncol, 16(1): 197-203, 1998.

49. Zagars, G. K.; Mullen, J. R.; and Pollack, A.: Malignant fibrous histiocytoma: outcome and prognostic factors following conservation surgery and radiotherapy. Int J Radiat Oncol Biol Phys, 34(5): 983-94, 1996.

V2N2 ESUN Copyright © 2005 Liddy Shriver Sarcoma Initiative.

Understanding the Diagnosis of
Undifferentiated Sarcomas: UPS vs. MFH

An ESUN Editorial
By Jeff Mito, BA and David Kirsch MD, PhD

It is not surprising that patients can find the current classification scheme for sarcomas complex and confusing. The World Health Organization (WHO) recognizes over 50 subtypes of soft tissue sarcoma, and some argue that there are more than 70. Many of these subtypes of sarcoma are classified, at least in part, according to the apparent line of differentiation of the tumor (the kind of normal cell that the tumor resembles). One particularly confusing diagnosis for patients is Malignant Fibrous Histiocytoma (MFH) or Undifferentiated Pleomorphic Sarcoma (UPS).

Historically, MFH was first described in the early 1960s based on cell culture experiments that showed sarcoma cells from these tumors grew in patterns similar to fibroblasts and behaved similarly to ‘histiocytic’ tissue resident immune cells, such as macrophages. This gave rise to the term MFH, which represented a morphologic description that included a diverse set of appearances, which sometimes overlapped with better-defined subtypes of soft tissue sarcoma.

By the 1980s, the diagnosis of MFH included five subtypes and became the most commonly diagnosed subtype of soft tissue sarcoma, despite the fact that it was primarily considered a diagnosis of exclusion (MFH was diagnosed only when the pathologist did not recognize the sarcoma as one of the other subtypes). Therefore, there are a number of clinical studies of sarcoma in the literature that include the outcome of patients diagnosed with MFH.

As scientific tools improved, new techniques were applied to MFH to try to subclassify this diverse set of tumors. Techniques like electron microscopy, immunohistochemistry, cytogenetics and, more recently, gene expression profiling have all attempted to subdivide MFH into better-defined subgroups. Studies that have utilized these tools have been successful in reclassifying many of the MFH tumors into other subtypes of soft tissue sarcoma. In time, the ability to reclassify MFH became accepted by many pathologists. Importantly, this re-classification was shown to have clinical relevance to patient outcome in some cases. Recognizing this, in 2002, the WHO classification of soft tissue sarcomas divided many of the subtypes that made up MFH into distinct subtypes of soft tissue sarcoma.

However, despite advances in diagnostics, there is still a group of soft tissue sarcomas that have no distinct line of differentiation to classify them more specifically. For these tumors, the WHO established a new term, UPS, which represents a diagnosis of exclusion. However, for historical reasons the term MFH was also maintained to show the evolution of this term to UPS. Therefore, patients may receive a diagnosis with any of these synonymous terms that are sometimes interchanged: Undifferentiated Pleomorphic Sarcoma (UPS), sarcoma not otherwise specified (NOS), and Malignant Fibrous Histiocytoma (MFH).

It is important for patients to recognize that, regardless of which of these diagnoses they receive, each represents a high-grade cancer that requires treatment. Given the challenge in classifying UPS and other soft tissue malignancies, applying the appropriate studies to identify these malignancies is important to accurately classify a patient’s tumor. As such, patients with soft tissue sarcomas should have their tumors examined by a pathologist with training in soft tissue tumors, and patients should be evaluated by a multidisciplinary team that specializes in soft tissue sarcomas.

Because recent studies suggest that UPS represents a common histologic appearance that may result from several different types of soft tissue tumors as they become "undifferentiated," in the future classifying these soft tissue sarcomas by examining the molecular characteristics of these tumors may provide important information for designing treatment. For example, pathologists might use gene sequencing technology to identify specific mutations that drive tumor development and maintenance. With these more advanced diagnostic approaches, it may be possible to identify specific targets for sarcoma therapy, which could lead to treatment based on specific gene mutations within the cancer rather than a therapy based on the specific subtype of soft tissue sarcoma, such as MFH or UPS.

This article is an opinion piece and has not been peer-reviewed.

By Jeff Mito, BA
MD/PhD student at Duke University in Durham, North Carolina

and David Kirsch MD, PhD
Associate Professor of Radiation Oncology and Pharmacology & Cancer Biology
Duke University in Durham, North Carolina

V9N5 ESUN Copyright © 2012 Liddy Shriver Sarcoma Initiative

Stories and Support

Diana, Malignant Fibrous Histiocytoma Survivor

Diana's Story

I was working as an ER nurse, and life was going quite smoothly for me and my family. One morning, as I was getting out of bed, my hand happened to brush against an unfamiliar lump on the side of my left leg, just 4 inches above the knee. It was painless, about half the size of a Silly Putty egg, and was easy to wiggle around. It seemed to have come out of nowhere.

Alarmed, I called my doctor and got in to her office that morning to get it checked out. She examined it, and said, "It looks like a lipoma to me." She explained that lipomas are benign lumps of fat tissue, and that no treatment is usually indicated. Still, she instructed, if the lump got bigger or became uncomfortable, she wanted to know about it.... Read Diana's story.

Lori, MFH survivor

Lori's Story

In May of 2000, everything I thought I knew about my life changed. I had just come home from a trip to New York to visit my grandparents. It was a very normal day, and while showering I noticed a pain in my right kidney area. "Great," I thought, "I’ve got a kidney infection." I went to my GYN, as he was my closest physician and the easiest place to get a urine test done. There was no infection, as it turned out, but I did have blood in my urine for no reason. He admitted me to run some tests. He scanned, x-rayed, scoped…you name it, he did it. Read Lori's story.

Find treatment and support resources

We maintain listings of sarcoma treatment centers, local support groups and organizations that provide financial assistance to sarcoma patients and their loved-ones.

Undifferentiated Pleomorphic Sarcoma Research

The Liddy Shriver Sarcoma Initiative is pleased to support UPS/MFH research. UPS is a rare tumor that usually affects adults. Treatment options include surgery, radiation therapy and chemotherapy. These treatments can increase survival but can also be very hard on the body. More effective and less damaging treatments are needed to save and improve the lives of those dealing with UPS.

The following research studies were funded by the Initiative after sarcoma experts agreed that they were clinically relevant and scientifically sound:

ImmunoSarc: The Immune Response in Sarcomas

ImmunoSarc: The Immune Response in Sarcomas$340,400 Grant: In this global collaborative study, Drs. Nielsen, Blay, Demicco, Maki, & Thomas aim to reveal the immune system's role in osteosarcoma and undifferentiated pleomorphic sarcoma and to build a foundation for the use of immunotherapy in sarcoma treatment.

This grant was funded by the Liddy Shriver Sarcoma Initiative, the Alan B. Slifka Foundation, and the Wendy Walk in October 2015.

Modeling Treatment Response of NF1-Deleted Sarcoma

Modeling Treatment Response of NF1-Deleted Sarcoma$69,000 Grant: In this study, investigators from Duke University will use their mouse model of NF1-deleted sarcomas to explore the role of NF1 mutations in the development and therapeutic response of rhabdomyosarcoma, undifferentiated pleomorphic sarcoma, and malignant peripheral nerve sheath tumor.

This grant was co-funded by the Liddy Shriver Sarcoma Initiative in April 2013. It was made possible by a generous gift from the Thumbs Up For Lane Goodwin Childhood Cancer Foundation and by donations made in honor of Brett Reed, Craig Dion, Denise Grove, Michael Cretella, and Samara Sheller.

MTAP Dysregulation in Osteosarcoma and MFH of the Bone

MTAP Dysregulation in Osteosarcoma $50,000 Grant: In this study, investigators from Mt. Sinai School of Medicine will build on their previous work on the MTAP gene in the hopes of identifying a target for the treatment of osteosarcoma and malignant fibrous histiocytoma of the bone.

This grant was co-funded by the Liddy Shriver Sarcoma Initiative in October 2012. It was made possible by generous gifts from Laura Somerville, Brandon’s Defense Foundation, Soccer ‘Round the Clock, Sarah’s Garden of Hope, and from the friends and families of Jonah Chrisman and Sara Corbelli.

Targeting the PI3K/AKT Pathway in UPS/MFH 

A Mouse Model of Chordoma$50,000 Grant: In this study, Drs. Torres, Zhu and Lev tested the use of PI3K/mTOR inhibitors on UPS/MFH cells. While studies in cell culture depicted a marked anti-UPS/MFH effect, only a delay in tumor growth was noted in vivo. It is possible that after more study, PI3K/mTOR inhibitors can be used in cominbation with other agents to increase their effectiveness.

This study was funded by the Liddy Shriver Sarcoma Initiative April 2010. It was made possible, in part, by a generous donation from Cliff and Arlene Blaker, and by donations made in memory of Ronald Rosenfeld.

Study of Tissue Samples in a Trial of Dasatinib

$25,000 Grant: This tissue study was performed in conjunction with a clinical trial on several types of sarcoma, including MPNST.


  • Figure 1
    Figure 1: A histologic specimen showing a classic storiform-pleomorphic malignant fibrous histiocytoma. Microscopically, the storiform pattern shows short fascicles of spindle cells radiating from a central point which is intermixed with neoplastic giant cells in the pleomorphic portion.
  • Figure 2: A histologic example of myxoid type MFH.
    In order for a tumor to be characterized as a myxoid variant, myxoid tissue must account for at least half of the tumor.
  • Figure 3: Clinical photograph of an MFH of the proximal lateral thigh.
  • Figure 4: Clinical picture of MFH in the hand.
  • Figure 5a: Axial MRI picture of an MFH in the thigh.
    The tumor is touching the femur bone but not invading into it. The location of the femoral artery and the femoral and sciatic nerves can be identified on MRI to allow for thorough operative planning.
  • Figure 5b: A coronal MRI picture of an MFH in the thigh.
    The MRI allows for accurate measurements of the size of the tumor.
  • Figure 6: Needle biopsy of an MFH in the thigh.
    Needle biopsies such as this one can often be performed in the clinic. It is important to draw out the incision which will be utilized to remove the tumor. The biopsy should then be obtained along that incision.
  • Figure 7: Limb sparing incision in the upper extremity for a sarcoma of the forearm.
    Biopsies must be performed along or directly parallel to an incision that allows for a limb sparing operation to remove the tumor. Note that an ellipse has been drawn around the previous biopsy incision. The biopsy tract should be excised at the time of definitive surgery to prevent local recurrence.
  • Figure 8
    Figure 8: Intra-operative photograph of an MFH of the scapula that was removed using limb salvage surgery. A cuff of normal tissue is kept with the mass so that the tumor is never actually exposed during the operation.
  • Figure 9: Brachytherapy catheters traversing the operative field.
    Once the tumor has been completely excised, radiation oncologists place empty tubes (catheters) at the base of the wound and sew the tubes into place. The wound is then carefully closed.