A case of orbital solitary fibrous tumor with fast-growing budding morphology.

Orbital solitary fibrous tumors (SFTs) are rare and are typically benign and slow‑growing. This report details a unique case of a rapidly progressing benign orbital SFT in a 75-year-old man with recurrent prostate cancer. Magnetic Resonance Imaging (MRI) initially revealed an extraconal mass, which, within five months, evolved significantly. Surgical excision revealed a primary encapsulated mass and a smaller, intimately attached, "budding" satellite nodule. Histopathology confirmed benign SFT characteristics with low mitotic activity and strong nuclear STAT6 and CD34 immunoreactivity. This case is notable for its rapid growth and presentation in an older patient with cancer, expanding the known morphological spectrum and growth kinetics of orbital SFTs. While the observation raises a hypothesis regarding potential systemic or hormonal influences, no receptor, molecular, or serum studies were performed to support a causal relationship. Overall, this case underscores the importance of thorough intraoperative exploration, continuous surveillance, and prompts further investigation into systemic or hormonal influences on SFT growth.