Ducto-lobular carcinoma in situ: Clinical and pathological findings in three cases with review of literature

Abstract

In situ carcinomas of the breast are traditionally divided into ductal and lobular based on a combination of morphological features. Ductal carcinoma in situ (DCIS) is further differentiated from lobular carcinoma in situ (LCIS) by the presence of membranous E-cadherin protein expression. The expression of this protein is lacking in the neoplastic cells of LCIS due to underlying molecular alterations in the E-cadherin gene (CDH1) but present in cases of DCIS. Pathologists frequently employ the use of E-cadherin immunohistochemistry as an ancillary aid to distinguish DCIS from LCIS in morphologically ambiguous cases. In a small minority of in situ carcinomas a dual population of neoplastic cells is present within the same terminal duct lobular unit with morphological and/or immunohistochmeical evidence of both ductal and lobular histology, an entity we and others refer to as ducto-lobular carcinoma in situ (DLCIS). Herein we describe three such cases in detail to include morphological features, E-cadherin immunohistochemical staining pattern, clinical history, management and follow-up. In addition a comprehensive review of the literature of such cases is summarised and an algorithmic approach to their future diagnosis proposed.