Malignant fibrous histiocytoma (MFH)
Malignant fibrous histiocytoma (MFH), now more accurately referred to as undifferentiated pleomorphic sarcoma (UPS), is a rare but aggressive soft-tissue sarcoma that constitutes about 1% of adult cancer diagnoses. Typically occurring in late adulthood, particularly peaking around the age of fifty, it most commonly arises in soft tissues such as fat, tendons, and ligaments, and can also be found in bone as osteosarcoma. The condition is noted for its high rate of recurrence and metastasis, particularly affecting the lungs and other organs. Risk factors include a history of radiation therapy, which can lead to the development of UPS seven to twenty years post-treatment, as well as prior conditions like retinoblastoma.
Clinically, UPS often presents as a painless, enlarging mass, and its diagnosis is best achieved through magnetic resonance imaging (MRI). Treatment typically involves surgical resection, with additional chemotherapy or radiation depending on the tumor's stage. Prognosis varies based on factors such as tumor size, depth, and metastasis, with a five-year survival rate ranging between 34% and 70% for advanced cases. Awareness of UPS is important for timely diagnosis and intervention, as the disease poses significant health challenges.
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Malignant fibrous histiocytoma (MFH)
ALSO KNOWN AS: (Formerly malignant fibrous histiocytoma (MFH)), sarcoma, histiocytoma, malignant fibrous histiocytoma
RELATED CONDITIONS: Lymphoma, multiple myeloma, hematologic diseases, retinoblastoma
DEFINITION: Undifferentiated pleomorphic sarcoma (UPS) is rare, accounting for around 1 percent of adult cancer diagnoses each year. However, it is the most common primary malignant soft-tissue tumor (sarcomas) of adulthood, occurring in fat, tendons, ligaments, cartilage, blood vessels, skin, and nerves. It can also be present in bone and is called osteosarcoma. It is usually seen in late adulthood, peaking at age fifty. These aggressive tumors tend to recur and metastasize.
The original name for UPS, malignant fibrous histiocytoma (MFH), was assigned because scientists thought it stemmed from histiocyte cells. However, further research revealed that mesenchymal stem cells are the most likely source of the disease.
Risk factors: UPS is the most common radiation-induced sarcoma. Anywhere a patient who previously received radiation therapy is vulnerable to UPS, which usually develops seven to twenty years after the therapy. Patients with retinoblastoma may develop UPS as a second cancer. Formation in bone is more frequent in White patients, with a male-to-female ratio of 1.5:1. Most often, UPS presents on the legs, arms, or abdomen.
Etiology and the disease process: UPS cells may derive from primitive mesenchymal cells, with four cell types predominating—storiform/pleomorphic, myxoid, giant cell, and inflammatory. The cells grow and spread quickly, impacting the lungs or other organs in 40 percent of cases.
Incidence: UPS accounts for 20 to 30 percent of all soft-tissue sarcomas. It is the most common malignant sarcoma in older adults. It often forms in soft tissue but can form in bone.
Symptoms: Soft-tissue UPS usually presents as a painless soft-tissue mass with progressive enlargement over months. Any deep-seated, painless, invasive intramuscular mass in patients over fifty is most likely UPS. Patients with retroperitoneal UPS have symptoms of fatigue, weight loss, abdominal pressure, fever, and malaise. Osseous UPS usually presents with pain over several months with or without swelling and can be associated with pathologic fracture. Most tumors are diagnosed when they reach around nine centimeters wide.
Screening and diagnosis: Soft-tissue malignant fibrous histiocytoma is best diagnosed with magnetic resonance imaging (MRI) with gadolinium contrast. This tumor usually appears as a well-defined hypervascular heterogeneous soft-tissue mass with areas of hemorrhage and necrosis. Osseous UPS usually presents as an aggressive Stage IIb lesion associated with pathologic fracture in approximately 20 percent of cases. Staging depends on pathology, compartmentalization, and the presence or absence of metastases:
- Stage Ia: Low grade, intracompartmental
- Stage Ib: Low grade, extracompartmental
- Stage IIa: High grade, intracompartmental
- Stage IIb: High grade, extracompartmental
- Stage III: Presence of metastases
Treatment and therapy: Treatment for Stage I tumors involves surgical resection with wide margins, whereas treatment for Stage II involves surgical resection with adjuvant radiation or chemotherapy.
Prognosis, prevention, and outcomes: Prognosis depends on tumor size, depth, location, histologic subtype, and presence of metastases. Local recurrence occurs in approximately 20 to 30 percent of cases. The five-year survival rate is between 34 and 70 percent for patients with Stage III tumors, but patients with small, low-grade tumors have a high chance of being cured. Metastases can occur in the lung, lymph nodes, bone, and liver.
Bibliography
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Fletcher, Christopher D. M. WHO Classification of Tumours: Soft Tissue and Bone Tumours. 5th ed. IARC, 2020.
Goldblum, John R., et al. Enzinger and Weiss's Soft Tissue Tumors. 7th ed. Elsevier Saunders, 2020.
Miyashita, Yudai, et al. “Primary Undifferentiated Pleomorphic Sarcoma (Malignant Fibrous Histiocytoma) of the Lung: A Case Report.” Clinical Case Reports, vol. 8, no. 1, 28 Nov. 2019, pp. 33-37. doi:10.1002/ccr3.2517.
Stump-Sutliff, K.A. "What Is Malignant Fibrous Histiocytoma in the Bones?" WebMD, 17 Apr. 2024, www.webmd.com/cancer/malignant-fibrous-histiocytoma-of-bone. Accessed 20 June 2024.
"Undifferentiated Pleomorphic Sarcoma." Cleveland Clinic, 21 Feb. 2022, my.clevelandclinic.org/health/diseases/22435-undifferentiated-pleomorphic-sarcoma. Accessed 20 June 2024.
Yamate, Jyoji. “Stem Cell Pathology: Histogenesis of Malignant Fibrous Histiocytoma and Characterization of Myofibroblasts Appearing in Fibrotic Lesions.” The Journal of Veterinary Medical Science, 2023, pp. 895–906, doi.org/10.1292/jvms.23-0225.