Multiply Recurrent Solitary Fibrous Tumor of the Orbit Without Malignant Degeneration: A 45-Year Clinicopathologic Case Study

Solitary fibrous tumor (SFT) is a rare mesenchymal spindle cell neoplasm originally described in the pleura and subsequently identified in a number of extrathoracic sites. Orbital SFT was first described in 1994; since then, more than 100 cases have been reported or reclassified with that diagnosis.^1- 2 Only 4 patients were younger than 10 years when first diagnosed as having orbital SFT. While most reports describe a benign clinical course, rare cases of primary malignant orbital SFT have also been documented. This led the World Health Organization to classify SFT as a neoplasm of intermediate biological potential (locally aggressive, rarely metastasizing).^3- 4 Increased cellular atypia or mitotic activity in recurrent lesions following primary excision of orbital SFTs has also been described, suggesting that complete initial resection is a critical prognostic factor in preventing malignant degeneration.^1,4- 7 We describe a patient with orbital SFT whose proptosis was first recognized at age 9 years and who underwent surgical excision at various institutions at ages 12, 22, and 52 years. To our knowledge, this represents the longest histopathologically documented follow-up of a patient with orbital SFT.