Recurrent Solitary Fibrous Tumors in the Orbit.

Background: Solitary fibrous tumors (SFTs) of the orbit are rare mesenchymal neoplasms that typically exhibit indolent behavior. However, a subset may recur, sometimes many years after initial treatment, posing significant diagnostic and therapeutic challenges. Because of the rarity of recurrent orbital SFTs, there is limited literature addressing their clinicopathologic features, diagnostic evolution, and optimal management strategies.

Objective: This study aims to analyse the clinical, radiologic, histopathologic, and immunohistochemical characteristics of 4 patients with recurrent orbital SFTs and to compare these findings with existing literature to elucidate prognostic factors and guide long-term management.

Methods: We retrospectively reviewed the clinical records of 4 patients with histologically confirmed recurrent orbital SFTs treated at our institution. Data regarding initial presentation, radiologic characteristics, histopathology, time to recurrence, mitotic activity, Ki-67 index, necrosis, and immunohistochemical profile were collected. All cases were evaluated for nuclear STAT6 expression, CD34 positivity, and proliferation index. A comparative review of previously published cases of recurrent orbital SFTs was conducted through the PubMed database.

Results: The recurrence interval ranged from 6 to 15 years. Initial diagnoses in 3 of the 4 cases were incorrect (hemangiopericytoma, Schwannoma, and cellular SFT), and were revised upon recurrence using updated immunohistochemistry. All cases demonstrated strong nuclear STAT6 and CD34 positivity on recurrence. Mitotic indices ranged from 0 to 10 per 10 high-power fields, and Ki-67 indices ranged from 2% to 40%. Necrosis was observed in one case only. Two patients required eyelid-sparing exenteration, whereas the others were managed with wide excision and orbital floor reconstruction. All patients remained recurrence-free at 2 to 3 years post-re-excision.

Conclusions: Recurrent orbital SFTs can present after a prolonged latency and may exhibit histologic evolution or diagnostic misclassification at initial presentation. Accurate diagnosis requires integration of histopathology with STAT6-based immunohistochemistry. Ki-67 and mitotic indices alone may not predict recurrence risk. Complete surgical excision remains the cornerstone of effective management. Our findings emphasize the importance of long-term surveillance and re-evaluation in cases with uncertain or evolving histopathologic features.