Annexin A10 is a marker for the serrated pathway of colorectal carcinoma

Serrated adenocarcinoma (SAC), representing at least 10 % of colorectal carcinomas (CRC), differs from conventional carcinomas not only by its histology, but also by its molecular basis. However, the diagnosis of SAC in poorly differentiated cases and without an adjacent serrated adenoma can be challenging. In this study, we utilized previously described expression data and identified annexin A10 (ANXA10) as a potential marker for SAC. We conducted ANXA10 immunohistochemistry in groups of 146 CRC patients and 131 serrated and conventional polyps. In CRC cases, ANXA10 expression associated with serrated histology (sensitivity 42 % and specificity 98 %). BRAF V600E mutation correlated with ANXA10 expression but also seven BRAF wild-type tumors (5 %) were positive for ANXA10. Immunoreactivity for either ANXA10 or BRAF V600E was an accurate predictor of serrated histology (sensitivity 55 % and specificity 97 %). ANXA10 expression did not associate with tumor stage or grade. Of the 131 colorectal polyps, 30/30 of sessile serrated adenomas, 6/11 traditional serrated adenomas, 20/32 hyperplastic polyps, and 2/27 tubulovillous adenomas were positive for ANXA10, while 31/31 tubular adenomas were negative. In conclusion, the results suggest that ANXA10 is a marker with high specificity for the serrated pathway of CRC.