Atypical Lobular Hyperplasia and Lobular Carcinoma In Situ

Atypical lobular hyperplasia (ALH) and lobular carcinoma in situ (LCIS) are lobular intraepithelial neoplasms that are often grouped under the term lobular neoplasia (LN). The pathognomonic feature of LN is discohesion secondary to absence or dysfunction of E-cadherin. LN is divided into classical and variant types and is considered to be both a risk factor and non-obligate precursor of invasive carcinoma. Classical LN is more common, shows indolent behavior, and is managed conservatively. Variant LN includes pleomorphic LCIS and florid LCIS, both of which have examples that would fall under the general category of “LCIS with necrosis.” Variant LN is uncommon and under recognized. Clinical data on variant LN is lacking, however the histology, biomarker profile, molecular alterations, and disease associations suggest a more aggressive disease than classical LN. Currently, there is no clear consensus on management of classical LN when diagnosed on core biopsy, whereas excision is recommended routinely for LN variants.