In situ and invasive lobular neoplasia of the breast.

Lobular neoplasia of the breast represents a group of related malignancies with clinical implications ranging from risk lesions [atypical lobular hyperplasia and lobular carcinoma in situ (LCIS)] through to aggressive invasive lesions, notably invasive pleomorphic lobular carcinoma. The diversity in lobular carcinoma is evident at the morphological level, at the molecular marker level and in cytogenetic profiles. Research in these areas is already changing the face of the disease group, for example suggesting that some lobular and ductal carcinomas are closely related and even that one of the lobular group, the tubulo-lobular carcinomas, should, in fact, be regarded as a ductal cancer. More research is required to understand the long-term pathogenic implications of a diagnosis of in situ lobular neoplasia, particularly pleomorphic LCIS, and to understand the genetics behind the well-recognized high risk of bilateral disease. For invasive carcinoma, molecular studies will allow refinement of therapy and the possibility of novel targeted therapies, for example directed against fibroblast growth factor receptor 1.