Sinonasal solitary fibrous tumour: A borderline entity with diagnostic challenges
Varun Kumar Singh, Mary Mathew, Ranjini Kudva, Kanthilatha Pai and Anjali Vijay
Sino nasal Solitary Fibrous Tumour (SFT) has been categorised as borderline/low-grade malignant tumours in the recent WHO classification of Head and Neck Tumours (2017). SFT have been reported in pleura and diverse extra pleural sites of which Sino nasal region accounts for <0.1%. Owing to its overlapping histopathological features with various oval/spindle cell lesions in the region, Sino nasal SFT often poses as a diagnostic dilemma.
Materials and methods: Eight cases diagnosed as Sino nasal SFT, over a period of twelve years (January 2006 - December 2017) were retrieved from the archives of Department of Pathology, Kasturba Medical College, Manipal and reviewed for clinical-morphological features.
Results: Sino nasal SFT was largely seen in males (M: F-3:1) with a median age of 54.5 years (33-74years). The predominant symptoms were nasal blockage, deviated nasal septum and occasional episodes of epistaxis. Grossly, the tumours appeared polypoidal to irregular masses, filling up the nasal cavity and extending to the nasopharynx and skull base. Microscopically, the tumours were composed of vague lobules of haphazardly arranged bland oval/spindle cells separated by collagen bundles and interspersed irregular vessels and were diffuse and strongly positive for CD34 on immunohistochemistry.
Conclusion: SFT is characterized by cytological bland spindle cells with scant cytoplasm separated by thick collagen bundles, arranged in variable architectural patterns. These features show considerable overlap with angiofibroma, leiomyoma, schwannoma and fibrous histiocytomas especially in the presence of high cellularity and hypo/ hyper cellular architecture. The diagnostic clues favouring SFT include bands of collagen and positivity for CD34 and Bcl2. SFT are tumours with borderline/ low-grade histology and can be managed by endoscopic resection. The poor prognostic indicators include old age, presence of tumour necrosis, >4 mitosis/10 HPF, and local recurrence is seen in 10-15% cases