Abstract
The purpose of the present report was to examine the possibility of molecular pathological subtyping of mucinous adenocarcinomas (MAC) of the colorectum. Thirty-five formalin-fixed and paraffin-embedded MAC specimens of the colorectum were analyzed. Genetic alterations of p53 gene and microsatellite instability (MSI) as well as immunohistochemical analysis of mucin subtypes (human gastric mucin (HGM), anti-mucin monoclonal antibody recognizing gastric gland mucous cells-1, MUC2, CD10) and expression levels of human mutL homolog 1 (hMLH1), p53 and Ki-67 were performed. According to MSI and p53 status, these tumors were subclassified into three groups: mutator-type tumors with a high frequency of MSI (20%), suppressor/p53-type tumors with p53 mutation, p53 overexpression or loss of heterozygosity of D17S250 (an adjacent locus to p53; 40%) and the unclassified tumors (40%). The suppressor/p53-type tumors had a significant association with distal colon location (P = 0.019), venous invasion (P = 0.002), extent of lymph node metastasis (P = 0.007) and higher tumor stage (P = 0.018). In contrast, mutator-type tumors had frequent expression of HGM (P = 0.005) and prominent lymphocytic infiltration at the advancing front of the tumor (P = 0.005). These results indicate that MAC of the colorectum could be subclassified according to molecular pathological background, reflecting distinct clinicopathological and phenotypic characteristics.
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