Lobular neoplasms and invasive lobular breast cancer

The term lobular neoplasia (LN) comprises both atypical lobular hyperplasia (ALH), and lobular carcinoma in situ (LCIS) and thus a spectrum of morphologically heterogeneous but clinically and biologically related lesions. LN is regarded as a nonobligatory precursor lesion of invasive breast cancer and at the same time as an indicator lesion for ipsilateral and contralateral breast cancer risk of the patient. Rare pleomorphic or florid variants of LCIS must be differentiated from classical LCIS. The classical type of invasive lobular carcinoma (ILC) can be distinguished from the non-special type of invasive breast cancer (NST) by E-cadherin inactivation, loss of E-cadherin related cell adhesion and the subsequent discohesive growth pattern. Variant forms of ILC may show different molecular features, and solid and pleomorphic differentiation patterns in cases of high grade variants. Important parameters for the prognostic assessment of ILC are tumor grading and the recognition of morphological variants.