Abstract
Purpose :
The classification of solitary fibrous tumour (SFT) and hemangiopericytoma (HPC) has greatly evolved in the past three decades. Based on immunohistochemical similarities, they were classified under the same pathologic entity, SFT/HPC, (2018 WHO Classification of Tumours of the Eye). The evolution of the nomenclature of SFT/HPC indicates the complexity of this rare entity. Previous reports have indicated that tumours with orbital and intracranial HPC pattern tend to be more aggressive than SFTs. We studied the histopathological and immunohistochemical characteristics of patients with orbital SFT/HPC and further classified this entity.
Methods :
We identified eight orbital SFT/HPC cases from the McGill University Health Centre’s ocular pathology laboratory in Montreal QC, from 2011 to 2019. Three had been previously diagnosed as HPC, five as SFT. The predominance of vascular proliferation with staghorn pattern (HPC) was assessed. The spindle morphology and the predominance of bundles of spindle cells (SFT) were also assessed. The cases were stained with the following antibodies: STAT6, CD34, Ki67, SMA, EMA, and S100 protein, and their characteristics were recorded.
Results :
A total of 8 patients were evaluated. The mean age of patients at time of surgery was 49 years and 7 were males. Follow up information available range from 6 to 96 months. In 3 patients (2 males and 1 female), the orbital biopsy revealed a predominant HPC pattern. The average age is 54 years (45 – 69). In 5 patients (all males), the average age is 46 years (31 – 63). The immunohistochemical characteristics of the 3 HPC showed negative STAT6, positive CD34, positive SMA, negative S100 and EMA. Ki67 was low (5-10%). The immunohistochemical characteristics of the 5 SFT revealed positive STAT6, positive CD34 (2 in the neoplastic spindle cells and vessels and 3 only in the vessels), positive SMA, negative S100 and EMA. Ki67 was low (5-20%).
Conclusions :
This case series confirms the pathological diversity of orbital SFT/HPCs. Patients with HPC tend to be older than patients with SFT without HPC pattern. The immunohistochemical panel is useful to further classify SFT/HPC with or without HPC pattern. Based on this histopathological and immunohistochemical study, it is important to diagnose two different types of SFT, with and without HPC pattern. Moreover, SFT with HPC pattern has a higher risk of local recurrences and late metastasis.
This is a 2020 ARVO Annual Meeting abstract.