Context: Lobular neoplasias (LNs) of the breast include atypical lobular neoplasia and lobular carcinoma in situ. Recent evidence suggests that LN is not only a risk factor for invasive lobular carcinoma, but is also a nonobligate precursor. Pleomorphic lobular carcinoma in situ (PLCIS) is a subtype of LN that has high-grade nuclei and other features that may mimic high-grade ductal carcinoma in situ. The management and follow-up of patients diagnosed with LN on core biopsy is a current issue of debate. However, recent genomic and molecular studies have identified candidate genes that may be important in understanding the pathogenesis of atypical lobular neoplasia and lobular carcinoma in situ, and thus may lead to other therapeutic interventions.
Objective: To review the literature on LN of the breast and discuss current issues in the diagnosis and management of this entity, with particular attention to the relatively newly recognized lesion PLCIS. Because the management of PLCIS varies from the other LN lesions, the recognition of PLCIS by the pathologist is necessary. Current issues in the molecular pathogenesis of LN are also presented.
Data sources: Extensive review of the literature. Hematoxylin-eosin-stained and immunohistochemical-stained tissue from the author's personal collection.
Conclusions: Although morphology and immunohistochemical stains, such as E-cadherin, are important in the diagnosis and understanding of LN, genomic and molecular studies may guide the way these lesions are handled in the future. Recognizing PLCIS is important both for patient management and for our future understanding of LN pathogenesis.