SWI/SNF Complex-Deficient Carcinoma Arising in the Lacrimal Drainage System

We present an SWItch/Sucrose NonFermentable (SWI/SNF) complex-deficient carcinoma centered in the lacrimal drainage system and orbit of a 76-year-old male. The patient presented with nasolacrimal duct obstruction, which persisted after dacryocystorhinostomy. Imaging and surgical exploration showed a 3-cm orbital mass centered around the lacrimal sac with involvement of the nasolacrimal duct and orbit. Microscopic examination revealed sheets, nests, and strands of poorly differentiated tumor cells. Some had enlarged hyperchromatic nuclei and eosinophilic cytoplasm, and others had round to oval, somewhat vesicular nuclei with paler cytoplasm. In situ carcinoma was present in the lacrimal sac lining, with invasion into adjacent structures. Immunohistochemical analysis showed loss of INI1 protein in the neoplastic cells, with retained expression in non-neoplastic stroma. While a few SWI/SNF complex-deficient sinonasal carcinomas have been shown to invade into the orbit, this case highlights the need to consider this rare entity in the differential diagnosis of tumors arising in the lacrimal drainage system.