Expression of cytokeratin 20 indicates invasive histological phenotype in poorly differentiated colorectal adenocarcinoma.

BACKGROUND/AIM Cytokeratin (CK) 20 expression is an independent prognostic factor of poorly differentiated adenocarcinoma (PDA) of the colon and rectum. We aimed to investigate the mechanism of its involvement through a clinicopathological study. PATIENTS AND METHODS We analyzed 156 surgically resected PDAs, which were sub-classified as solid type (Por1) showing expansive growth, or non-solid type (Por2) showing infiltrative growth. Associations of CK20 expression with morphological features and molecular markers were analyzed. RESULTS CK20(+) PDA (n=91) was associated with more advanced disease stage and unfavorable prognosis compared with CK20(-) PDA (n=65). Pathologically, CK20(+) PDA was significantly associated with p53 overexpression, Por2, abundant fibrous stroma, and stepwise de-differentiation, while CK20(-) PDA was significantly associated with mismatch repair deficiency, Por1, sparse fibrous stroma, and de novo histogenesis. CONCLUSION CK20 expression in PDA is closely associated with invasive histological features, providing prognostic significance, and may also point to a specific histogenetic pathway.