SMARCA4-deficient undifferentiated gastric carcinoma: a case series and literature review.

Undifferentiated gastric carcinoma, characterized by anaplastic cells lacking distinct features of cytological or architectural differentiation, poses diagnostic and therapeutic challenges. Recent studies have suggested an association between this carcinoma and deficiencies in the SWI/SNF complex, particularly mutations in subunits such as SMARCA4. We herein report six cases of SMARCA4-deficient undifferentiated gastric carcinoma with molecular findings, highlighting the rarity and diagnostic pitfalls of this malignancy. Predominantly occurring in males over 50 years, these cases presented with nonspecific symptoms and were often diagnosed at an advanced stage. Histologically, the tumors exhibited a sheet-like growth pattern, reduced or absent epithelial markers, and loss of BRG-1 expression, with molecular analysis confirming SMARCA4 gene mutations. The response to conventional chemotherapy was poor, underscoring the importance of complete surgical resection and the development of alternative treatment modalities.