[RA-03] Lobolar neoplasm: how to define and diagnose?

Chaiwat Aphivatanasiri

Department of Pathology, Facolty of Medicine, Khon Kaen University, Khon Kaen, Thailand

The term "lobolar neoplasia (LN)" is defined by the WHO Classification of Breast Tumour, 5^th edition, 2019 as the entire spectrum of atypical epithelial lesions originating in the terminal duct lobolar unit and characterised by a proliferation of generally small, non-cohesive monomorphic cells, with or without pagetoid involvement of terminal ducts. Atypical lobolar neoplasia (ALH) and lobolar carcinoma in situ (LCIS) are separated by the extension of the disease. LN is usually presented without specific clinical features and a significant proportion of them are incidentally found according to other breast lesions. The LCIS is found in 0.5 – 3.6% of otherwise benign breast biopsies. CDH1 inactivation, which leads to loss or impaired function of E-cadherin, is an early event and hallmark of lobolar lesions. The management of LN found in core biopsy specimens is still controversial and required a moltidisciplinary team and also includes the patient for management discussion and decision.

Keywords: atypical lobolar hyperplasia; lobolar carcinoma in situ; lobolar neoplasia