Abstract
300 Background: Ampullary adenocarcinoma (AA) is a rare entity. AA can originate from either intestinal or pancreaticobiliary ductal epithelium, and patients are often managed as those with pancreaticobiliary carcinomas. The study objectives were the genetic profiling of AA and the identification of specific molecular profiles according to these 2 pathological types. Methods: AA patients included in the AGEO retrospective multicenter cohort who underwent surgical resection of their tumor between 1999 and 2010 were selected. Formalin-fixed, paraffin-embedded (FFPE) archival tissue blocks were collected. Next generation sequencing (NGS) using a 50 gene panel (Ion AmpliSeq Cancer panel) on tumor DNA, and immunohistochemistry (IHC) panel including CK7, CK20, MUC1, MUC2 and CDX2, on tumor sections, were performed. Results: NGS was performed on 101 tumors from 6 hospitals, with 1 technical failure. In total, the most frequent gene mutations were: KRAS (45%), TP53 (40%), APC (15%), PIK3CA (12%), SMAD4 (9%), BRAF (8%), CDKN2A (6%). No mutation was found in 21% of tumors. According to IHC, the most common histological type was intestinal (51%), followed by pancreaticobiliary type (42%) and undetermined (7%). BRAF mutation was significantly associated with intestinal type (8 vs 0, p = 0.017). According to Cosmic database, similarities of molecular profiles exist between AA with intestinal type and colorectal adenocarcinoma, and between AA with pancreaticobiliary type and pancreas adenocarcinoma, respectively. Conclusions: This study shows that AA is a heterogeneous entity and that a large proportion of AA presents a molecular profile that is more similar to that of colorectal adenocarcinoma, compared to pancreatic adenocarcinoma. This important information could be interesting to guide treatment decision in patients with this rare disease.
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