SMARCA4 Deficient Gastric Carcinoma With Squamous Differentiation in a Young Patient With Aggressive Clinical Course

Inactivation of SMARCA4 (BRG1), a subunit of SWI/SNF complex, has been reported in malignancies from various sites, including the thorax, uterus, ovary, and gastrointestinal tract, and is usually associated with aggressive clinical course. These tumors have been reported primarily in elderly patients and on histology demonstrate high-grade morphology, often with rhabdoid differentiation. SMARCA4 loss is exceedingly rare in primary gastric cancers. Here, we present a unique example of SMARCA4 deficient gastric carcinoma in a 28-year-old male patient with molecular confirmation which showed a poorly differentiated histology and focal squamous differentiation. Despite multidisciplinary management, including FOLFOX chemotherapy, immunotherapy (nivolumab), and surgical resection, the patient succumbed to his disease within 2 years of diagnosis. This case report highlights the aggressive nature of SMARCA4-deficient carcinomas, which are often resistant to conventional chemotherapy, and underscores the importance of early diagnosis and exploring alternative therapeutic approaches for such malignancies.