Malignant Undifferentiated and Rhabdoid Tumors of the Gastroesophageal Junction and Esophagus with SMARCA4 Loss: A Case Series.

Undifferentiated SMARCA-4 deficient carcinoma of the esophagus and gastroesophageal junction is a rare, highly aggressive and diagnostically challenging malignancy. Here we present a case series of high-grade undifferentiated malignant neoplasms of the esophagus and gastroesophageal junction that share SMARCA4 loss by immunohistochemistry and demonstrate a rhabdoid phenotype. Five cases are presented, including 4 men and 1 woman with an age range of 48-79 years. Interestingly, only one case showed intestinal metaplasia (Barrett esophagus) and no cases demonstrated glandular dysplasia or glandular differentiation. In all, the lesional cells were immunoreactive with antibodies to keratins (3/5), CD34 (2/4), and CD138 (4/5). SMARCA4 expression was diffusely lost in all cases whereas SMARCB1 expression was intact. OncoScan assay demonstrated loss of SMARCA4 in all cases analyzed. Additional OncoScan findings included abnormalities of CDKN2A in 2/3 cases, abnormalities of TP53 in 2/3 cases, and abnormalities of PTPRD in 2/3 cases, among other abnormalities.