Gastrointestinal pathology

Background: The Switch/Sucrose Nonfermentable (SWI/SNF) complex is a chromatin remodeling system involved in regulating key cellular functions, including proliferation and differentiation.Loss of one or more of its subunits has been observed in undifferentiated carcinomas of the gastrointestinal tract. 1 We present a case of SMARCA4 and SMARCA2 co-deficient undifferentiated carcinoma of the gastro-oesophageal junction (GOJ) and stomach.Case report: A 76-year-old male presented with dysphagia and was found to have severe ulcerative oesophagitis and gastric fundal fold thickening on endoscopy.Histopathological examination of the biopsy revealed infiltrative atypical cells with large pleomorphic nuclei, prominent nucleoli, and occasional rhabdoid cells.Immunohistochemistry showed loss of expression of epithelial, melanocytic, muscle, and haematolymphoid markers in the atypical cells.Further testing demonstrated loss of nuclear expression of SMARCA4 and SMARCA2, leading to the diagnosis of SMARCA4 and SMARCA2 co-deficient undifferentiated carcinoma of the GOJ and stomach.Discussion: SWI/SNF complex-deficient undifferentiated carcinomas of the GI tract are rare, aggressive tumors that lack a specific line of differentiation. 2,3 Diagnosing these tumors requires the exclusion of morphological mimics and a high index of suspicion to prompt testing for SWI/SNF subunits. 1,2 Given their poor response to traditional chemotherapy and the potential for response to targeted treatments, timely and accurate diagnosis is critical for optimal patient management. 1