SMARCB1/INI1 Deficient Sino-Nasal Carcinoma: Extending the Histomorphological Features

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.

SMARCB1 (INI-1)-Deficient Sinonasal Carcinoma: A Systematic Review and Pooled Analysis of Treatment Outcomes

“…Of the remaining 192 patients, 72 patients whose individual baseline patient characteristics, treatment details, and survival outcomes could not be identified and verified [2,16,19,20,23,[28][29][30]34,35,38], and they were thus not included into our survival analysis. As a result, only 120 patients with data availability of baseline patient characteristics, disease stage, and survival outcomes in 25 publications were included for survival and prognostic factor analyses [1,2,11,[13][14][15][16][17]19,[21][22][23][24][25][26][27][31][32][33]36,37,[39][40][41][42]. Meanwhile, our institution had eight patients who had a complete set of baseline characteristics, treatment details, and survival outcomes, and who were treated between 2014 and 2021.…”

SMARCB1-deficient sinonasal carcinoma: a case report and literature review

“…Since that report, Ayyanar et al. argued that as the number of reported cases has increased, the morphological spectrum of this tumor has gradually expanded [ 9 ]. Many different morphological features have been described in the recent literature.…”

Proceedings of the North American Society of Head and Neck Pathology, Los Angeles, CA, March 20, 2022: SWI/SNF-deficient Sinonasal Neoplasms: An Overview

“…Loss of SMARCB1 because of biallelic inactivation of its gene in a subset of poorly or undifferentiated sinonasal carcinoma has been first described in 2014 by two independent groups, followed by a few additional series including one large multi-institutional series (n=39) [7,8]. To date, <150 cases have been reported [7][8][9][10][11][12].…”

“…However, frankly squamous cell features and keratinization are absent. A smaller fraction of cases (30%) displays a "pinkish" eosinophilic, plasmacytoid/ rhabdoid cell morphology [7][8][9][10][11][12]. Scattered plasmacytoid and rhabdoid cells can be identified, also in the basaloid tumors, upon scrutiny [25].…”