Pseudo-micropapillary structures associated with columnar cell lesions of the breast are an artifact due to traumatic epithelial detachment: a potential pitfall which can lead to overtreatment

Abstract

Dear Editor, Columnar cell lesions (CCLs) of the breast including flat epithelial atypia (FEA) are believed to be nonobligatory precursors of a low-nuclear-grade breast neoplasia family [1]. They are detected increasingly in needle core biopsies because of the presence of microcalcifications observed on screening mammography. Here, we report a hitherto undescribed artifact associated with CCLs of the breast, which superficially resembles micropapillary atypical ductal hyperplasia (ADH) or low-grade ductal carcinoma in situ (DCIS). The complexity of this artifact varies widely from a simple fold to a complex labyrinthine-like structure. If the latter is confused with genuine micropapillary structures or Roman bridges, overtreatment can occur because management of patients differs between pure CCLs and those associated with ADH/low-grade DCIS, especially when found in needle core biopsies. We have recently observed two cases of CCL of the breast that showed complex pseudo-micropapillary structures protruding into the duct lumen. Based on histopathological and immunohistochemical findings, we infer that these structures are not a true micropapillary overgrowth but an artifact, which originates from folding and adhesion of epithelial sheets detached from CCLs. The first case concerns a 49-year-old Japanese woman whose screening mammography revealed microcalcifications in the left breast. Vacuum-assisted needle core biopsy (VAB) was performed because the microcalcifications varied in size and shape and were localized to the upper half of the breast in a segmental fashion. The VAB was composed of 12 fragments of breast tissue. Four fragments contained CCLs; variably distended ductules were lined by columnar epithelial cells with apical cytoplasmic snouts (Fig. 1a–c). In the lumina of some dilated ductules, racetracks were seen or ribbon-like bridges continuous with the epithelial lining of CCL. These pseudo-micropapillary structures lacked fibrovascular cores and contained two epithelial layers. The cells were similar to luminal cells of CCL (Fig. 1c). Immunohistochemical staining with cytokeratin 5/6 demonstrated a few myoepithelial cells attached to the basal S. Ichihara (*) : S. Moritani :M. Hasegawa Department of Pathology, Nagoya Medical Center, 4-1-1 Sannomaru Naka-ku Nagoya, 460-0001 Aichi, Japan e-mail: shu-kkr@umin.ac.jp