Myxofibrosarcoma

Myxofibrosarcoma is a rare type of cancer that arises from the connective tissue, specifically from the fibrous tissue. It is classified as a soft tissue sarcoma and is also known as myxoid malignant fibrous histiocytoma.

Definition and Classification

Myxofibrosarcoma is defined as a malignant tumor that consists of a mixture of myxoid (mucous-like) and fibrous components. It is classified into three grades based on the degree of cellular atypia, mitotic activity, and the presence of necrosis: low-grade, intermediate-grade, and high-grade.

Clinical Features

Myxofibrosarcoma typically presents as a slowly growing, painless mass in the subcutaneous tissue or deep soft tissue. The most common locations are the extremities, particularly the thigh and leg, followed by the trunk and retroperitoneum. The tumor can range in size from a few centimeters to over 10 cm in diameter.

Pathological Features

The pathological features of myxofibrosarcoma include a mixture of myxoid and fibrous areas, with a variable degree of cellular atypia. The tumor cells are typically spindle-shaped or stellate, with a high nuclear-to-cytoplasmic ratio. Mitotic figures can be numerous, and necrosis may be present.

Immunohistochemistry

Immunohistochemical studies have shown that myxofibrosarcoma cells express vimentin, a marker of mesenchymal differentiation, as well as other markers such as CD34 and factor XIIIa. However, the tumor cells are typically negative for S-100 protein, desmin, and cytokeratins.

Treatment and Prognosis

The treatment of myxofibrosarcoma usually involves wide local excision or amputation, depending on the size and location of the tumor. Adjuvant radiation therapy may be used to reduce the risk of local recurrence. The prognosis is generally poor, with a high rate of local recurrence and metastasis, particularly to the lungs.

Epidemiology

Myxofibrosarcoma is a rare tumor, accounting for less than 1% of all soft tissue sarcomas. It occurs more frequently in older adults, with a peak incidence in the seventh and eighth decades of life. There is no significant gender predilection.

Molecular Genetics

Recent studies have identified several genetic alterations in myxofibrosarcoma, including mutations in the TP53 tumor suppressor gene and the MDM2 oncogene. However, the molecular pathogenesis of this tumor remains poorly understood.