The Spectrum of Columnar Cell Lesions

Abstract

Columnar cell lesions encompass a group of epithelial proliferations that arise within dilated acini in terminal duct lobular units. Columnar cell lesions have undergone different classifications and have been referred to by a variety of other names in the earlier literature. The current World Health Organization (WHO) classification includes the non-atypical columnar cell lesions—columnar cell change and columnar cell hyperplasia, and atypical forms—columnar cell change and columnar cell hyperplasia with cytologic atypia, which are collectively referred to as flat epithelial atypia. Columnar cell lesions are frequently the targeted lesions in stereotactic biopsies performed for mammographic calcifications. With the increased use of screening imaging and advances in mammography, these lesions are commonly encountered in the core biopsy setting. Most studies addressing the clinical significance of columnar cell lesions have focused on the immediate concern of whether or not to excise these lesions, particularly flat epithelial atypia, when diagnosed in a core biopsy sample. This chapter will review the relevant clinical and histopathologic features of columnar cell lesions, the microscopic differential diagnoses, and management of columnar cell lesions diagnosed in a core biopsy.