Mammographically detected in situ lobular carcinomas of the breast.

We present ten cases of mammographically detected lobular carcinoma in situ (LCIS), involving a single area of variable size (up to a quadrant) in seven cases and the entire gland in three cases. Histologically, calcifications were associated with necrotic central areas within the in situ carcinomatous foci. Multiple foci of LCIS were observed in all five cases in which mastectomy had been performed. Cytologically, the lesions were characterized by a solid proliferation of round noncohesive cells with nuclei of intermediate size. Immunocytochemically, all cases were E-cadherin and p53 negative, and c-ErbB-2, GCDFP-15 and estrogen receptor positive. The proliferation index, evaluated with Ki67, was in the low range. Four cases were associated with foci of infiltrating lobular carcinoma (ILC). These findings contradict the commonly held opinion that LCIS is not mammographically detectable because of its lack of necrosis and calcification. This study documents the existence of a variant of LCIS exhibiting the mammographic features and central necrosis classically associated with ductal carcinoma in situ (DCIS), while retaining the spatial distribution, cytological composition and immunocytochemical features of lobular carcinoma.