Immunohistochemical survey of pS2 expression in intraductal lesions associated with invasive ductal carcinoma of the breast.

We examined the expression of pS2 protein in 48 invasive ductal breast carcinomas with an extensive intraductal component, using immunohistochemical staining of paraffin-embedded sections. The patients selected for this study would have met the criteria for breast-conserving surgery applied at our institute at present. The rate of pS2 expression in the intraductal lesion was significantly higher than that in the main invasive lesion. The incidence of pS2 protein expression in the latter lesions was very similar to that in invasive carcinoma without intraductal lesions. The pS2 positivity of the intraductal lesion was equal to or higher than that of the invasive lesion. Of intraductal lesions, those classified as non-comedo carcinomas frequently contained more pS2 protein than did comedo carcinomas.