Undetected invasive lobular carcinoma of the breast: Review of false-negative smears

Analysis of a series of 34 fine-needle aspirations (FNA) from 28 patients w ith invasive lobular carcinoma (ILC) was undertaken. The false-negative sme ars were reviewed to reveal the cause of such a relatively frequent error. This was a retrospective study and comparison between the cytological and p athological findings in a series of 34 FNA. Three cases were excluded witho ut sufficient material. Twelve cases were positive, nine suspicious of mali gnancy, and 10 were considered false-negatives. In a second analysis of thi s later group, one was reclassified as carcinoma, two reconsidered without sufficient material for diagnosis, and the remaining seven, still considere d negatives, constituted the core of this study. Of these seven, there were none with hypercellular smears and in six there was a predominance of fat- tissue fragments. The scarce epithelial component showed honeycomb-flat she ets in four, loose clusters in three, small and tight clusters with irregul ar limits in six, and more than 10% of isolated epithelial cells (noncohesi ve cells) in one case. "Staghorns" were undetected and myoepithelial cell n uclei were very scarce in all cases. Some nuclear enlargement was detected in one, angulated nuclear contour in three, and nuclear crowding was presen t in five.. All seven had fine, homogeneous chromatin, without prominent nu cleoli. Cytoplasmic limits were undefined in all but one (6/7) and occasion al cytoplasmic vacuolization was detected in two. Hypocellular smears with few, small, and dense groups (bur always with more than 10 groups in at lea st one smear) can be related with ILC. In these cases, further studies are recommended to exclude malignancy. The loose cluster and flat sheets identi fied in four cases represent a benign epithelial hyperplasia mixed with the ILC. Diagn. Cytopathol. 2000;23:303-307. (C) 2000 Wiley-Liss, Inc.