SMARCB1/INI1 Deficient Sino-Nasal Carcinoma: Extending the Histomorphological Features
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ORIGINAL PAPER
SMARCB1/INI1 Deficient Sino‑Nasal Carcinoma: Extending the Histomorphological Features Pavithra Ayyanar1 · Pritinanda Mishra1 · Chappity Preetam2 · Amit Kumar Adhya1 Received: 25 July 2020 / Revised: 7 October 2020 / Accepted: 23 October 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract SMARCB1/INI1 deficient sinonasal carcinoma is a variant of sinonasal undifferentiated carcinoma (SNUC). There is a paucity of literature describing the histomorphological features of this relatively new entity. Herein we describe the histomorphological features of three such cases and review the literature. We retrospectively reviewed the cases of SNUC diagnosed in our institute in the last 6 years. Immunohistochemistry for INI1, NUT & p16 were performed on these cases. Three cases showed loss of INI1. The histomorphology and clinicopathological features of these cases were studied and compared with non INI1 deficient SNUC. A total of 9 cases of SNUC were identified. Three of these cases showed loss of INI1. These three cases had presented with large sinonasal mass and with intracranial extension. Histopathology of these cases showed a diffuse infiltrative pattern, nest, and islands of predominantly basaloid cells with focal rhabdoid morphology. Additional features like small cell carcinoma like pattern, pseudoalveolar and pseudoglandular patterns, clear vacuoles and pseudopapillary appearance were also noted. We conclude that in presence of a mixed pattern of cells with a predominance of basaloid morphology, the possibility of SMARCB1/INI1 deficient sinonasal carcinoma must be strongly suspected and immunohistochemistry for INI1 must be performed. Keywords Sinonasal undifferentiated carcinoma · SMARCB1/INI1 deficient sinonasal carcinoma · Basaloid morphology · Rhabdoid morphology · p16
Introduction Sinonasal undifferentiated carcinoma (SNUC) is defined as an undifferentiated carcinoma of the sinonasal tract without glandular and squamous features and not otherwise classifiable [1]. SNUC is rare, with about 0.02 cases per 100,000 people, accounting for only about 3–5% of all sinonasal carcinomas. There is no etiological role of EBV or HPV in SNUC.
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s12105-020-01246-9) contains supplementary material, which is available to authorized users. * Amit Kumar Adhya [email protected] 1
Department of Pathology and Lab Medicine, All India Institute of Medical Sciences, Bhubaneswar, Odisha 751019, India
Department of ENT, All India Institute of Medical Sciences, Bhubaneswar, Odisha, India
2
Recent molecular studies have identified various variants of SNUC, which include NUT carcinoma, SMARCB1 (INI1)–deficient sinonasal carcinoma (SDSC), and SMARCA4 (BRG1)–deficient sinonasal carcinoma [2–4]. These molecular alterations can be therapeutically targeted and hence the necessity of distinguishing them from SNUC. SMARCB1/INI1 deficient sinonasal carcinoma is an uncommon and recently descri
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