Atypical lobular hyperplasia and lobular carcinoma in situ: surgical and molecular pathology

Lobular carcinoma in situ and atypical lobular hyperplasia were first descr ibed over 50 years ago. Despite this long incubation period, the biological nature of the lesions remains controversial. They are generally regarded a s 'risk indicators' of invasive cancer rather than true precursor lesions. When first described, the 'carcinoma in situ' designation implied radical t reatment in the form of mastectomy. Subsequent observation has shown that t he lesions are often multifocal and bilateral. The risk to the woman of dev eloping invasive cancer after a diagnosis of lobular carcinoma in situ is s mall. Hence, the lesion has increasingly been regarded as a 'hyperplastic' proliferation, which although predicting for subsequent risk of invasive ca ncer, does not in itself need treatment. In this review, we challenge this view and explore the developments in the understanding of this controversia l entity.