Frequent nuclear beta-catenin accumulation and associated mutations in endometrioid-type endometrial and ovarian carcinomas with squamous differentiation

Focal squamous differentiation is a common feature of endometrioid endometrial and ovarian carcinomas (E-Em and E-Ova Cas). A close association between mutated beta-catenin accumulation and alteration in cellular morphology has recently been demonstrated in murine L cell lines. To clarify the possible role of beta-catenin abnormalities and changes in tumour morphology, 60 grade (G) 1 or G2 E-Em Cas with areas of squamous differentiation (SqD), including morules and squamous metaplastic (SqM) foci, as well as 32 G1 or G2 tumours without such lesions, were investigated and the results compared with findings for c-jun and wnt-1 expression. Twenty-three E-Ova Cas, with and without SqD lesions, were also examined. In E-Em Cas, frequent nuclear beta-catenin accumulation was observed in 22 (84.6%) of 26 tumours with morules and 15 (45.5%) of 33 with SqM foci, in contrast to 4 (12.5%) of 32 without such lesions. Similar findings were also noted for mutations in exon 3 of the beta-catenin gene, involving codons 32, 33, 34, 37, 41, and 45, the single nucleotide substitutions being identical between SqD and the surrounding carcinoma tissue in most informative cases. The mutations were positively related to nuclear immunopositivity, but inversely to membrane expression, while there was no association with the status of c-jun or wnt-1. These E-Ova Cas, nuclear beta-catenin accumulation and mutations were limited to tumours with SqD features, independent of c-jun and wnt-1 status. These data indicate that beta-catenin abnormalities are relatively common in E-Em and E-Ova Cas with SqD features, implying a role in the squamous differentiation of tumour cells, not necessarily related to c-jun and/or wnt-1 status.