Low-grade fibromyxoid sarcoma

Low-grade fibromyxoid sarcoma (LGFMS) is a rare type of soft tissue sarcoma that typically presents as a slow-growing, painless mass. It was first described by Evans HL in 1987. Despite its benign appearance, LGFMS can metastasize many years after initial diagnosis, often to the lungs.

Clinical presentation

Patients with LGFMS often present with a slow-growing, painless mass. The tumor can occur anywhere in the body, but it is most commonly found in the deep soft tissues of the extremities, particularly the thigh. Other common sites include the trunk and the neck. LGFMS can occur at any age, but it is most common in young adults.

Pathology

On gross examination, LGFMS is typically a well-circumscribed, lobulated mass with a grey-white cut surface. Microscopically, the tumor is composed of bland spindle cells arranged in a whorled pattern, with alternating areas of fibrous and myxoid stroma. The tumor cells have small, uniform nuclei and scant cytoplasm. Mitotic figures are rare. Immunohistochemically, the tumor cells are usually positive for vimentin and negative for S100, desmin, and smooth muscle actin.

Diagnosis

The diagnosis of LGFMS is based on the characteristic histologic and immunohistochemical features. However, the diagnosis can be challenging due to the tumor's bland appearance and slow growth. Molecular testing can be helpful in confirming the diagnosis. The most common genetic alteration in LGFMS is a fusion of the FUS and CREB3L2 genes.

Treatment

The mainstay of treatment for LGFMS is surgical resection with clear margins. Radiation therapy may be used in cases where complete surgical resection is not possible. Chemotherapy is generally not effective for LGFMS.

Prognosis

The prognosis for patients with LGFMS is generally good, with a 5-year survival rate of over 90%. However, the tumor can metastasize many years after initial diagnosis, often to the lungs. Regular follow-up is therefore important for patients with LGFMS.

See also

• Soft tissue sarcoma
• FUS gene
• CREB3L2

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