Cytomorphologic findings of SMARCA4-deficient thoracic sarcoma/carcinoma: Report of two cases

Abstract

Introduction/Objective SMARCA4-deficient thoracic sarcoma/carcinoma is a highly aggressive neoplasm characterized by SMARCA4 (chromatin remodeling complex) deficiency. It affects mostly smokers (85%) with a broad age range of presentation (mean age: 50 years). Most patients present with advanced disease and extensive involvement of thoracic structures. The cytomorphologic features of this entity have not been fully described. Methods/Case Report A 59-year-old female, former smoker, with a prior history of lung adenocarcinoma, presented with a new 2.8 cm right infrahilar nodule concerning for recurrence. The second patient, a 54-year-old male who is a smoker, presented with an 8.0 cm right perihilar mass extending into the right lung and mediastinum with encasement of the right main pulmonary artery. Cytologically, the smears from both aspirates were comprised of single cells and loosely cohesive clusters of ovoid to spindle cells with scant to moderate cytoplasm, stippled chromatin, and focally prominent nucleoli. Numerous mitotic figures were appreciated. Necrosis was present within the smear background. The cell block sections showed tumor cells arranged in glandular and focal papillary architecture with a myxoid background. In one case, intermediate to large-sized cells with focal cytoplasmic clearing and patchy extracellular metachromatic material were also noted. Rhabdoid morphology was not appreciated. Immunohistochemically, the tumor cells were at least focally positive for vimentin, TLE-1, SALL4, CK AE1/AE3 and TTF-1, while being negative for CK7, CK20, Napsin-A, SOX-10, p40 and neuroendocrine markers. Both tumors showed SMARCA4 (BRG1) loss of expression. Results (if a Case Study enter NA) N/A Conclusion While the cytomorphologic findings of SMARCA4-deficient thoracic sarcomas/carcinomas are not specific, the FNA diagnosis should be considered for any poorly differentiated neoplasm involving the lungs or mediastinum which should prompt an appropriate immunocytochemical work-up that includes SMARCA4/BRG1 assessment