Gastric SMARCA4-deficient undifferentiated tumors: clinicopathological analysis of two cases in a single center

Large SMARCA4-deficient tumors are more likely to have massive necrosis on the surface, leading to negative biopsy results. This tumor has a diffuse lamellar growth and needs to be differentiated from a variety of tumors with similar morphology, such as lymphoma, malignant melanoma, neuroendocrine carcinoma and undifferentiated sarcoma. The tumor cells were negative or only slightly positive for CKpan increases the difficulty of pathological diagnosis of this disease. However, loss of BRG1 (SMARCA4) expression can confirm the diagnosis. Chemotherapy combined with anti-PD1 treatment may have potential benefits in the management of gastric SMARCA4-deficient undifferentiated tumors. However, given the rarity of these tumors and the limited number of cases in our study, further research with larger cohorts is needed to validate these preliminary results.