Histologic phenotypes of colonic carcinoma in Sweden and in Japan.

The occurrence of predominant histologic phenotypes in overt colonic carcinomas from two disparate geographical regions were analyzed. A total of 424 overt colonic carcinomas (223 in Swedish and 201 in Japanese patients) were classified into predominant phenotypes (i.e. comprising > 50% of the tumor). Six predominant phenotypes were found: tubular, serrated-microcystic, villous, fenestrated, signet ring cell and undifferentiated. A predominant phenotype was present in 57.3% (n = 243) of the 424 tumors (in 55.2% of the 223 tumors from Swedish patients and in 61.7% of the 201 tumors from Japanese patients). The serrated-microglandular phenotype was significantly more frequent in Japanese than in Swedish patients. Environmental and/or ethnic factors may be the possible cause(s) for that difference. The frequency of regional lymph node tumor spread (Dukes C) was significantly lower in serrated-microglandular and in villous phenotypes than in undifferentiated-signet ring cell types, despite that patients harbouring either one of the two former phenotypes were among the oldest in the whole series. Serrated-microglandular and villous colonic cancer phenotypes may carry a better prognosis (independently of their degree of histologic differentiation or age) since they are less prone to metastasize to regional lymph nodes than undifferentiated-signet ring cell phenotypes.