Lobular neoplasia displaying central necrosis: a potential diagnostic pitfall.

The distinction between intraepithelial proliferations of ductal and lobular type is often straightforward. However, a small number of cases create diagnostic problems even for experienced pathologists. Among those is the recognized, but not always kept in mind, lobular neoplasia with "comedo-type" necrosis. Herein, we present six cases of lobular neoplasia with comedo necrosis. Three cases were classified correctly, whereas the three remaining cases were initially misdiagnosed as ductal carcinoma in situ with necrosis. Of these three misdiagnosed cases, one patient underwent radiation therapy before this study was carried out. The two other patients were correctly reclassified as lobular type in subsequent excisional biopsies. One case showed a focus of microinvasion. All six lesions were negative by E-cadherin immunohistochemistry. Our experience highlights that the correct differentiation between intraepithelial neoplasias of ductal and lobular type may be challenging, and that the correct differentiation is extremely important for prognostic information and therapeutic decisions.