Abstract

Tan PH
Department of Pathology, Singapore General Hospital

Columnar cell lesions (CCL) of the breast refer to a spectrum of benign to atypical entities having in common variably dilated terminal duct lobular units lined by columnar epithelial cells with prominent apical cytoplasmic snouts. They are increasingly encountered in breast biopsies as a result of their associated microcalcifications being detected on mammographic screening.

CCL represent a new challenge in breast pathology. Many are benign histologically and biologically, others display cytologic atypia, and yet there are those that disclose both cytologic and architectural alterations that place them into the category of ductal carcinoma in situ (DCIS). For CCL with cytologic atypia, a major issue is in the reproducible recognition of the degree of atypia on core biopsies that would warrant a further excision biopsy, as this has implications of cost and anxiety for affected women. CCL with cytologic atypia are also referred to as flat epithelial atypia. There is emerging evidence to suggest that flat epithelial atypia may represent a precursor of or the earliest morphologically recognisable form of low-grade ductal carcinoma in situ. They are often associated with tubular carcinomas and lobular neoplasia. It is this category of flat epithelial atypia that poses the greatest problem in breast screening, as its finding on preoperative core biopsies often requires an open excision to exclude a more sinister lesion, yet there is currently a lack of established criteria to define what constitutes significant atypia. More work has to be done to refine diagnostic guidelines for this group of lesions.