Clinical, histopathological, cytogenetic and prognostic differences between mucinous and nonmucinous colorectal adenocarcinomas.

OBJECTIVE: To assess the clinical and biological significance of histological typing of colorectal carcinomas. PATIENTS AND METHODS: The retrospective analysis of 142 consecutive patients who underwent surgical resection of a mucinous (MC; n = 27; 19%) or a nonmucinous (nMC; n = 115; 81%) colorectal adenocarcinoma was carried out. The two groups were compared in terms of the clinical features, p53 gene expression (antiserum CM1), proliferating cell nuclear antigen (PCNA) labeling index, DNA ploidy (by flow cytometry), histopathological features, prognosis and recurrence rate.
RESULTS: The two types of tumors differed with respect to patient age, location, morphology, pattern of genetic lesions and type of tumor recurrences. Twenty-five percent of the patients with MC and 9% of those with nMC (p = 0.04) were under 50 years of age. The incidences of right MC and left MC were similar, while the majority of the nMC were located on the left side (p = 0.04). The MC were of higher grade and their margins more infiltrative than those of the nMC (p = 0.001 and p = 0.01, respectively), p53 nuclear staining was observed less frequently in the MC than in the nMC (30% vs 55%; p = 0.03). The PCNA labeling index was higher in the nMC (46% vs 21%; p = 0.05). We observed no significant differences with respect to tumor stage, incidence of vascular invasion or prevalence of lymphocytic infiltration. The prognosis was similar in both groups, although their recurrence patterns differed, with a tendency toward locoregional recurrence in the cases of MC.
CONCLUSION: These findings suggest that, despite their similar prognoses, these two types of lesions are epidemiologically, phenotypically and genotypically different and, thus, result from distinct carcinogenic pathways.