A case report of SMARCA4-deficient undifferentiated gastric carcinoma diagnosed by endoscopic ultrasound-guided fine needle aspiration

Gastric SMARCA4-deficient undifferentiated carcinoma is an exceptionally rare and highly aggressive malignancy characterized by loss of SMARCA4 expression. Due to its rarity and nonspecific clinical presentation, it poses considerable challenges for diagnosis and management. In this study, we describe the case of a 55-year-old man who was admitted after an incidental finding of a retroperitoneal mass. Contrast-enhanced abdominal computed tomography (CT) and magnetic resonance imaging (MRI) revealed a soft-tissue lesion located in the hepatogastric region. Endoscopic ultrasound (EUS) was subsequently performed to assess the lesion further, enabling precise evaluation of the depth of invasion and facilitating tissue acquisition via EUS-guided fine-needle aspiration (FNA). Cytological examination and immunohistochemical analysis of the EUS-FNA specimen confirmed the diagnosis of SMARCA4-deficient undifferentiated gastric carcinoma. Following disclosure of the pathological diagnosis, the patient declined further treatment and chose to discontinue medical care. He died one month later during follow-up. This case underscores the importance of clinical awareness and prompt diagnostic evaluation, particularly the value of EUS-FNA, in the early identification of SMARCA4-deficient undifferentiated gastric carcinoma, which may ultimately contribute to improved clinical outcomes.