The clinicopathological significance of micropapillary pattern in colorectal cancers

The aim of the present study is to elucidate the clinicopathological significance and prognostic role of micropapillary pattern (MPP) in colorectal cancer (CRC). We investigated the correlation between the presence of MPP and clinicopathological characteristics and prognosis in 266 CRCs. In addition, the clinicopathological significance of MPP in mucin pools was investigated and compared to pure MPP, which is not associated with mucin pools. MPP, regardless of its proportion in the overall tumor, was found in 74 of 266 CRCs (27.8%). The rate of MPP in proportions ≥5% was 9.4% (25 of 266 cases). CRC with MPP showed higher rates of vascular and lymphatic invasion, higher metastatic lymph node ratio, and higher pT stage compared to CRC without MPP. In addition, increasing proportion of MPP in overall tumor showed more frequent vascular and lymphatic invasions (P = .002 and P = .008, respectively). Among 74 CRCs with MPP, 25 CRCs were found in mucin pools (33.8%). These cases were more right-sided and poorly differentiated with less frequent lymphatic invasion and lymph node metastasis, compared to CRCs with pure MPP. The presence of MPP significantly correlated with worse overall survival (P = .010). In 74 CRCs with MPP, overall survival significantly differed between pure MPP and MPP in mucin pools (P = .003). Taken together, our data suggest that the presence of MPP significantly correlated with aggressive tumor behavior and worse survival in CRC. In addition, the clinicopathological significance of MPP in mucin pools differed from CRC with pure MPP.