Validity of pathological diagnosis for early colorectal cancer in genetic background

BACKGROUND: This study aimed to investigate the validity of pathological diagnosis of early CRC (E‐CRC) from the genetic background by comparing data of E‐CRC to colorectal adenoma (CRA) and The Cancer Genome Atlas (TCGA) on advanced CRC (AD‐CRC). METHODS: TCGA data on AD‐CRC were studied in silico, whereas by next‐generation sequencer, DNA target sequences were performed for endoscopically obtained CRA and E‐CRC samples. Immunohistochemical staining of mismatch repair genes and methylation of MLH1 was also performed. The presence of oncogenic mutation according to OncoKB for the genes of the Wnt, MAPK, and cell‐cycle–signaling pathways was compared among CRA, E‐CRC, and AD‐CRC. RESULTS: The study included 22 CRA and 30 E‐CRC lesions from the Chiba University Hospital and 212 AD‐CRC lesions from TCGA data. Regarding the number of lesions with driver mutations in the Wnt and cell‐cycle–signaling pathways, E‐CRC was comparable to AD‐CRC, but was significantly greater than CRA. CRA had significantly more lesions with a driver mutation for the Wnt signaling pathway only, versus E‐CRC. CONCLUSIONS: In conclusion, the definition of E‐CRC according to the Japanese criteria had a different genetic profile from CRA and was more similar to AD‐CRC. Based on the main pathway, it seemed reasonable to classify E‐CRC as adenocarcinoma. The pathological diagnosis of E‐CRC according to Japanese definition seemed to be valid from a genetic point of view.