Solitary fibrous tumor

Solitary fibrous tumor (SFT), also known as solitary fibrous tumor/hemangiopericytoma, is a rare mesenchymal neoplasm of fibroblastic origin that can arise in virtually any anatomical location. It was originally described in the pleura but is now recognized to occur in extrapleural sites including the meninges, orbit, peritoneum, pelvis, soft tissues of the extremities, and other organs. SFT is characterized by a distinctive NAB2-STAT6 gene fusion resulting from an intrachromosomal inversion on chromosome 12q13, which serves as a hallmark molecular feature and diagnostic marker. Most solitary fibrous tumors present as slow-growing, painless masses. When arising in the pleura, patients may experience cough, chest pain, or dyspnea. Some patients develop paraneoplastic hypoglycemia (Doege-Potter syndrome) due to tumor secretion of insulin-like growth factor II. While the majority of SFTs behave in a benign or indolent fashion, approximately 10-20% may exhibit malignant behavior with local recurrence or distant metastasis. Malignant features include increased cellularity, nuclear atypia, high mitotic activity, tumor necrosis, and infiltrative margins. The primary treatment for solitary fibrous tumor is complete surgical resection with clear margins, which is curative in most cases. For unresectable, recurrent, or metastatic disease, treatment options include radiation therapy and systemic therapies. Antiangiogenic agents such as temozolomide combined with bevacizumab, pazopanib, and other tyrosine kinase inhibitors have shown activity in advanced SFT. Long-term follow-up is recommended for all patients, as late recurrences can occur even decades after initial treatment. Prognosis is generally favorable for completely resected tumors, but malignant variants carry a more guarded outlook.

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