A Rare Case of Solitary Fibrous Tumor Involving the Nasolacrimal Duct System in a 12-Year-Old Female: A Case Report and Review of the Literature

We report the youngest case of solitary fibrous tumor (SFT) with extensive involvement of the nasolacrimal duct system and discuss current literature regarding this tumor type. A 12-year-old female presented with a 6-month history of an enlarging right medial orbit mass. CT orbits revealed a well-circumscribed, enhancing lesion adjacent to the right nasolacrimal system. Pathology confirmed SFT (1.2 × 1.1 × 1.1 cm) with spindle cell morphology and a mitotic rate of 5 per 10 high power fields. Immunohistochemistry (IHC) was positive for CD-34 and signal transducer and activator of transcription 6 and negative for S-100, consistent with SFT. Next-generation sequencing confirmed NGFI-A-binding protein 2::signal transducer and activator of transcription 6 gene fusion. To our knowledge, only 17 cases of SFT involving the lacrimal sac have been reported, of which, the average age was 43.5 years. Notably, SFTs with a high mitotic rate carry a heightened risk of malignant transformation. Given our patient's mitotic rate of 5 per 10 high power fields, positive surgical margins, and young age, close follow-up is imperative.