Mesenteric SMARCA2-Deficient Yet SMARCA4-Preserved Aggressive Undifferentiated Tumor: A Case Report.

Area of Science:

• Oncology
• Genetics
• Chromatin Biology

Background:

• The SWItch Sucrose Non-Fermentable (SWI/SNF) complex, involving SMARCA4 and SMARCA2, regulates gene expression and is linked to cancer.
• Thoracic SMARCA4-deficient undifferentiated tumors are a recognized WHO classification, but abdominal rhabdoid tumors are poorly understood.

Observation:

• A mesenteric solid tumor in a man in his 70s presented with rapid progression and bowel obstruction.
• Histopathology revealed a rhabdoid tumor with a high Ki67 index.
• Immunohistochemistry showed SMARCA2 deficiency with preserved SMARCA4 expression and absent Claudin-4.

Findings:

• This is the first reported case of a mesenteric undifferentiated tumor with rhabdoid cytomorphology due to isolated SMARCA2 deficiency within the SWI/SNF complex.
• The tumor exhibited SMARCA2 deficiency while SMARCA4 expression was preserved.
• The patient experienced aggressive peritonitis carcinomatosis post-surgery.

Implications:

• This case suggests that abdominal tumors with rhabdoid features may arise from similar oncogenic pathways as thoracic SMARCA4-deficient tumors.
• Further investigation is crucial to elucidate the clinical characteristics, molecular mechanisms, and therapeutic strategies for these rare abdominal SWI/SNF-deficient tumors.
• Understanding these rare entities contributes to the broader knowledge of SWI/SNF-related carcinogenesis.