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Aims: To determine whether the dissociation of tumour cells from neoplastic glands in colorectal carcinomas is caused by disruption of the wnt-signalling pathway and whether the adenomatous polyposis coli (APC) protein is implicated in this. Methods and results: In a series of 99 clinically sporadic colorectal carcinomas, APC exon 15 mutations, loss of heterozygosity (LOH) and promoter methylation were found in 49, 20 and 23 cases, respectively. Singly, these APC aberrations were not associated with the degree of tumour cell dissociation, but dissociation was higher for the cases with combined APC mutation and LOH. Immunohistochemical β-catenin translocation to the nucleus correlated with APC aberrations. Tumour growth pattern (expansive/infiltrative/diffuse) and tumour stroma (desmoplastic common-type versus keloid-like) showed a statistically significant association with tumour cell dissociation and with β-catenin translocation. Of other molecular alterations tested ( p53 mutation; LOH at 17p13, 18q, 9p21; CpG island methylator phenotype), only the highly microsatellite unstable status ( n = 11) was negatively associated. Conclusions: In colorectal carcinomas, wnt dysregulation relates to APC aberrations, but wnt dysregulation and APC aberrations are not strictly required for tumour cell dissociation, and additional and/or alternative factors must play a role. Of these, outside-in signalling by cancer cell–matrix interactions, as partially mirrored in histomorphological features, could be important. [ABSTRACT FROM AUTHOR]