Definition and Overview

Malignant fibrous histiocytoma (MFH) is a type of soft tissue sarcoma, a group of rare malignant tumours that occurs in different parts of the body and characterised by fracture, pain, and swelling. The term MFH was first used in the 1960s to describe a histiocytes-rich tumour with a storiform growth pattern. However, following a number of studies, the cell origin of the condition was disputed and the concept of fibrohistiocytic differentiation was challenged. For this reason, the condition was declassified and was renamed pleomorphic undifferentiated sarcoma (PUS) by the World Health Organisation (WHO). The new term provides an accurate description of the condition without implying the origin of tumour cells.

As with other types of sarcoma, which accounts for just 1% of all cancers, PUS is very rare with just a few thousand diagnoses every year. Due to the limited number of cases, the condition remains an enigma and is yet to be fully understood by the medical community.

PUS commonly occurs in the abdomen and extremities but it can also develop in other parts of the body, presenting as a painless mass of soft tissue. It has the tendency to spread to the lungs when not treated early. A large number of cases have been observed in patients over 50 years old. PUS has been described as highly aggressive and most likely to metastasise and recur following a successful treatment.

Causes of Condition

MFH is a cancerous tumour that commonly starts in soft tissues that support, surround or connect organs and body parts. It can also develop in bone. Its exact causes are not entirely understood and its exact origin remains unidentified.

However, scientists believe that the following play a role in the development of the disease:

  • Exposure to certain chemicals including but not limited to arsenic, vinyl chloride, and wood preservatives

  • History of multiple myeloma and sickle cell disease

  • Paget’s disease or fibrous dysplasia of the bone

  • Radiation treatment for Hodgkin disease, retinoblastoma, and breast cancer

Key Symptoms

Malignant fibrous histiocytoma symptoms are not noticeable at the onset of the disease because the tumour affects elastic tissue that can be easily moved. For this reason, the tumour may exist and grow quite large before it is discovered. Symptoms usually show when the tumour starts to compress surrounding structures. When this happens, patients notice:

  • A painless, growing palpable mass

  • Soreness caused by compressed muscles or nerves

  • Difficulty walking if the tumour is found on the legs

  • Decreased range of motion

Some patients also experience chills, fever, night sweats, and unexplained weight loss.

The symptoms mentioned above are not definitive signs of MFH. Other conditions that are less serious can also produce such symptoms. To get a diagnosis and to rule out sarcoma, patients must see a doctor as soon as possible.

Who to See and Types of Treatments Available

Patients with lumps and bumps are encouraged to seek medical attention as soon as possible. This is essential especially if the mass is growing and causing symptoms. To assess the condition, doctors perform a thorough physical examination and imaging tests including an X-ray and magnetic resonance imaging (MRI) or computed tomography (CT) scan. These help identify the tumour’s location, its size, and whether it is in close proximity to neurovascular structures. Patients diagnosed with MFH are referred to sarcoma specialists for treatment.

To determine the most appropriate malignant fibrous histiocytoma treatment, doctors determine the stage of cancer by performing positron emission tomography (PET) or CT scan.

  • Stage 1 MFH - Localised low to intermediate grade tumour

  • Stages 2 and 3 MFH - Localised but a higher grade of tumour

  • Stage IV - Metastatic cancer that has spread to lymph nodes and other sites of the body

Doctors also determine the grade of tumour, which is the most important indicator of malignant fibrous histiocytoma prognosis.

  • Grade 1 - The tumour is less likely to grow and spread to other areas of the body

  • Grade 2 - The tumour has a moderate likelihood of growing and spreading

  • Grade 3 - More likely to grow and metastasise or spread to other parts of the body

Malignant fibrous histiocytoma of bone and soft tissues are commonly treated with surgery. The goal of the procedure is to remove the entire tumour along with a wide margin of surrounding healthy tissue. As much as possible, doctors perform a procedure called limb-sparing surgery to avoid amputation.

If surgery is not possible due to the tumour’s location or the patient’s overall health condition, chemotherapy is performed. The procedure uses medications to minimise the risk of cancer spread or recurrence by killing malignant cells.

Radiation therapy is also commonly used in cancer treatment. The procedure kills cancer cells or prevents them from growing using radiation. Many studies have shown that radiation has successfully decreased the risk of recurrence in the original site.

In some cases, chemotherapy or radiation therapy is performed before surgery to shrink the tumour so it can be safely and easily removed during a surgical procedure.

The five-year malignant fibrous histiocytoma survival rate is generally low (50-60%) for patients with a high-grade tumour or those with stage III or IV of the disease. Low-grade tumours, on the other hand, are mostly cured by surgery.

References:

  • Barkley, H. T., Jr.; Martin, R. G.; Romsdahl, M. M.; Lindberg, R.; and Zagars, G. K.: Treatment of soft tissue sarcomas by preoperative irradiation and conservative surgical resection. Int J Radiat Oncol Biol Phys, 14(4): 693-9, 1988

  • Pezzi CM, Rawlings MS Jr, Esgro JJ, Pollock RE, Romsdahl MM.; Prognostic factors in 227 patients with malignant fibrous histiocytoma. Cancer. 1992 Apr 15;69(8):2098-103

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