P-146 The first comprehensive genomic characterization of rectal squamous cell carcinoma

Rectal cancers represent 35% of colorectal cancers; 90% are adenocarcinomas while rectal squamous cell carcinomas represents 0.3% them. Given its rarity, little is known concerning pathogenesis, molecular profile and therapeutic management. The current treatment trend to treat carcinoma by analogy with anal definitive chemoradiotherapy setting aside surgery in case local recurrence. We performed an in-depth genomic analysis (Next Generation Sequencing – 400 gene panel, Oncoscan, Human Papilloma Virus characterization) on 10 samples compared them silico those adenocarcinoma. shows 100% HPV positivity. It has a similar mutational (PIK3CA, PTEN, TP53, ATM, BCL6, SOX2) copy number variations profiles (3p deletion 3q, 5p, 8q, 20p gain) carcinomas. PI3K/Akt/mTOR the most commonly affected signaling pathway similarly carcinoma. In addition, common alterations seen adenocarcinoma (FLT3, CDX2, GNAS BCL2, SMAD4, MALT1 mutations) were not found these cases. This study presents first comprehensive characterization confirm existence this rare histology similarity proximity confirms adequacy management based localization.