Orbital solitary fibrous tumor – Case series and new perspectives

Abstract

AbstractPurpose To present a case series of orbital solitary fibrous tumour (OSFT) from a tertiary referral centre focussing on diagnostic features including assessment of STAT6, a recently described antibody for immunohistochemistry (IHC) in which positivity is said to indicate NAB2‐STAT6 gene fusion.Methods This is a retrospective case series. Among all orbital tumours resected between 2001‐2014, 12 OSFT cases were identified. Data collected included patient demographics, clinical presentation, morphological and IHC features, management and clinical outcome. IHC for STAT6 was also performed in other soft tissue tumours to assess its specificity.Results There were 3 males and 9 females. The average age was 46 years (18 – 81). The mean follow‐up was 39.3 months (3‐156 months). Presenting symptoms included proptosis(n=6), periocular mass(n=4), foreign body sensation(n=1), and epiphora(n=3). Cellularity, hyalinisation and myxoid areas were variable. Necrosis was seen in one recurrent case. Giant cells were present in 3 cases. <4/10HPF mitoses were seen in 6 cases. All cases showed diffuse strong nuclear positivity with STAT6. In contrast, STAT6 expression was not demonstrated in other pathologies (e.g. neurofibroma, schwannoma, haemangioma, nodular fasciitis). CD34, CD99 and BCL2 ware positive in most cases but with varied staining pattern. One case was CD31 positive and 2 cases expressed SMA focally. All cases underwent elective surgical resection or debulking with complete histopathological clearance in 6 cases.Conclusion This case series confirms previously described variation in presentation and management challenges associated with OSFT. STAT6 antibody can be a helpful adjuvant in the diagnosis of OSFT.