Mixed apocrine/endocrine ductal carcinoma in situ of the breast coexistentwith lobular carcinoma in situ

An unusual mixed form of ductal carcinoma in situ (DCIS) of the breast is d escribed, which exhibits a biphenotypic morphology encompassing a range of differential diagnostic DCIS subtypes. In adddition, immunophenotypic and u ltrastructural studies demonstrate neuroendocrine and apocrine differentiat ion, raising questions regarding appropriate classification and biological behaviour. In two cases, coexistence of this mixed form of DCIS with lobula r carcinoma in situ (LCIS) in the same duct lobular units is an additional unusual feature that might, at least in some cases, indicate a closer relat ion between them.