~ 316 ~ International Journal of Clinical and Diagnostic Pathology 2019; 2(1): 316-320 ISSN (P): 2617-7226 ISSN (E): 2617-7234 www.patholjournal.com 2019; 2(1): 316-320 Received: 20-11-2018 Accepted: 22-12-2018 Varun Kumar Singh Department of Pathology, Melaka Manipal Medical College, Manipal campus, Manipal Academy of Higher Education, Manipal, Udupi, Karnataka, India Mary Mathew Department of Pathology, Kasturba Medical College, Manipal, Manipal Academy of Higher Education, Manipal, Udupi, Karnataka, India Ranjini Kudva Department of Pathology, Kasturba Medical College, Manipal, Manipal Academy of Higher Education, Manipal, Udupi, Karnataka, India Kanthilatha Pai Department of Pathology, Kasturba Medical College, Manipal, Manipal Academy of Higher Education, Manipal, Udupi, Karnataka, India Anjali Vijay Department of Pathology, Melaka Manipal Medical College, Manipal campus, Manipal Academy of Higher Education, Manipal, Udupi, Karnataka, India Correspondence Anjali Vijay Department of Pathology, Melaka Manipal Medical College, Manipal campus, Manipal Academy of Higher Education, Manipal, Udupi, Karnataka, India Sinonasal solitary fibrous tumour: A borderline entity with diagnostic challenges Varun Kumar Singh, Mary Mathew, Ranjini Kudva, Kanthilatha Pai, and Anjali Vijay DOI: https://doi.org/10.33545/pathol.2019.v2.i1e.47 Abstract Introduction: 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. Keywords: Solitary fibrous tumour, Sino nasal tumour, CD34, STAT6, borderline tumour Introduction Solitary fibrous tumour (SFT) is a mesenchymal tumour, first described in 1942 by Stout and Murrey [1] . Word Health Organisation in 2017 revised the classification of Sino nasal tumours and Sino nasal hemangiopericytoma as SFT. These tumours were classified under the borderline/ low malignant potential tumours along with desmoid-type fibromatosis, glomangiopericytoma and hemagioendothelioma [2] . Primarily a tumour of the pleura, SFT is seen most commonly in the pleural and abdominal cavity, followed by extremities; head and neck SFT account for around 12% of all the cases [3, 4] . Sino nasal SFT are unusual and account of <0.1% of all cases and owing to their overlapping morphological features with other spindle cell mesenchymal lesions in the region, presents as a diagnostic dilemma. Most of the Sino nasal SFT behave in a benign manner; however, a few case reports have documented an increased local recurrence and metastasis associated with them [5] . Here we present eight cases of Sino nasal SFT with their clinicopathological features and follow up to further the understanding of these uncommon tumours. Materials and methods: Eight cases diagnosed as SFT in the Sino nasal region over a period of twelve years (January 2006-December 2017) were included in the study. Following permission from the institutional ethics committee, the clinical and demographic data were retrieved from the electronic medical records.