[Concepts and problems of lobular neoplasia].

The term lobular neoplasia (LN) includes lobular carcinoma in situ (LCIS) and atypical lobular neoplasia (ALH). It is generally considered to be a risk lesion and a non-obligatory precursor for the subsequent development of an invasive carcinoma in the ipsilateral or contralateral breast. LN has also been termed lobular intraepithelial neoplasia (LIN). A grading system (LIN 1-LIN 3) has been suggested as a tool for a more precise estimation of the individual risk. When LN is the most significant finding in a core biopsy, the probability of a higher grade lesion is about 17% in the follow-up surgical biopsy, justifying follow-up surgery in the majority of cases. A higher risk of progression is attributed to LIN 3 (pleomorphic LN, extensive LN, and signet ring cell LN) compared to LIN 1 or LIN 2. These special forms of LN may have an unusual presentation clinically or histologically. Using immunohistology, LN are characterized by the loss of E-cadherin, low proliferative activity and by positive hormone receptor status. The molecular characteristics of LN are similar to those of invasive lobular carcinomas, indicating the nature of LN as a precursor lesion.