作者
Abbas Agaimy,Ondřej Daum,Bruno Märkl,Ines Lichtmannegger,Michal Michal,Arndt Hartmann
摘要
Undifferentiated gastrointestinal tract carcinomas are rare highly aggressive neoplasms with frequent but not obligatory rhabdoid features. Recent studies showed loss of SMARCB1 (INI1), a core subunit of the SWI/SNF chromatin remodeling complex, in 50% of tested cases. However, the molecular pathways underlying histologically similar but SMARCB1-intact cases are unknown. We herein analyzed 13 cases for expression of 4 SWI/SNF complex subunits SMARCB1, SMARCA2, SMARCA4, and ARID1A and the mismatch-repair proteins MLH1, MSH2, MSH6, and PMS2 by immunohistochemistry. Patients included 12 men and 1 woman aged 32 to 81 years (median, 57 y). Site of origin was colon (5), small bowel (2), stomach (3), small+large intestine (1), small intestine+ampulla of Vater (1), and esophagogastric junction (1). All tumors showed anaplastic large to medium-sized cells with variable rhabdoid features, pleomorphic giant cells, and, rarely, spindle cell foci. Abortive gland formation was seen in 3 cases and bona fide glandular component in 1 case. Most cases strongly expressed vimentin and variably pancytokeratin. In total, 12/13 cases (92%) showed loss of at least 1 SWI/SNF component. Loss of SMARCB1 (5/13), SMARCA2 (10/13), SMARCA4 (2/13), and ARID1A (2/13) was observed either in combination or isolated. SMARCA2 loss was isolated in 5 cases and coexisted with lost SMARCB1 in 5 cases (all 5 SMARCB1-deficient tumors showed loss of SMARCA2 as well). Co-inactivation of SMARCB1 and SMARCA4 or of SMARCA2 and SMARCA4 was not observed. Two mismatch-repair-deficient cases (MLH1/PMS2) showed concurrent loss of SMARCB1, SMARCA2, and (one of them) ARID1A. This study illustrates for the first time loss of different components of the SWI/SNF complex other than SMARCB1 in undifferentiated gastrointestinal carcinomas including novel SMARCA4-deficient and SMARCA2-deficient cases. Our results underline the close link between SWI/SNF deficiency and the aggressive rhabdoid phenotype. Frequent loss of SMARCA2 possibly points to fragility/vulnerability of the SWI/SNF complex as a consequence of lost core subunit SMARCB1. The exact molecular mechanisms underlying co-inactivation of different SWI/SNF subunits merit further investigations.