[Gastrointestinal tumors with SWI/SNF complex deficiency: a clinicopathological analysis of 36 cases]

Objective: To investigate the clinicopathological characteristics of gastrointestinal tumors with SWI/SNF complex deficiency and to perform a prognostic analysis of the patients. Methods: Gastrointestinal tumor cases with SWI/SNF complex deficiency expression diagnosed at the Department of Pathology, Zhongshan Hospital, Fudan University, Shanghai, China from August 2021 to May 2023 were collected. Hematoxylin and eosin (HE) stained slides were reviewed, and immunohistochemical results were analyzed. Clinical and pathological information was recorded, and relevant literature was reviewed. Results: A total of 36 cases of gastrointestinal tumor with loss of SWI/SNF complex expression were identified, including 28 males (77.8%) and 8 females (22.2%). The average age at diagnosis was 70 years (range 48-85 years). Clinical staging showed 3 cases in stage Ⅰ (8.3%), 12 cases in stage Ⅱ (33.3%), 19 cases in stage Ⅲ (52.8%), and 2 cases in stage Ⅳ (5.6%). Complete or partial loss of ARID1A expression was observed in 20 cases (55.6%); complete or partial loss of SMARCA2 expression was observed in 24 cases (66.7%). SMARCA4 exhibited complete loss of expression in 4 cases (11.1%). Eleven cases (30.6%) showed concurrent complete or partial losses of both ARID1A and SMARCA2 expression. Twelve cases (33.3%) had mismatch repair protein deficiency, all of which were characterized by MLH1/PMS2 absence. Mismatch repair protein deficiency was associated with loss of ARID1A expression (P<0.01). Patients with mismatch repair protein deficiency were also associated with earlier clinical stage and a lower risk of lymph node metastasis compared to the ones with intact mismatch repair proteins (P<0.05). Conclusions: SWI/SNF complex deficiency in gastrointestinal tumors is associated with dedifferentiation and often accompanied by mismatch repair protein deficiency. Compared to the cases with intact mismatch repair proteins, the cases with defective mismatch repair protein have an earlier clinical stage and a lower risk of lymph node metastasis.