Breast fine-needle aspiration. A comparison of thin-layer and conventional preparation.

Two hundred forty-two breast fine-needle aspirates prepared by the Cytyc ThinPrep Processor were compared with aspirates prepared by the conventional smear method. Palpable and nonpalpable mammographic breast lesions were aspirated and the first half of the aspirate was submitted for conventional smears and the second half was rinsed into a proprietary fixative and loaded on the ThinPrep Processor for monolayer slide preparation. The matched pairs were diagnosed and analyzed separately in a double-blinded manner and later paired for comparison. Diagnoses correlated exactly in 62% of cases. The diagnosis of fibroadenoma was made in only 4 of 21 cases on ThinPrep (19% correlation). Semiquantitative analysis of several cytologic features indicated potential pitfalls for accurate diagnosis using the ThinPrep Processor. These included loss of background constituents (such as stroma and adipose tissue), decreased cellularity and single ductal epithelial cells, and decreased cytologic detail including size, shape and nuclear texture. The ThinPrep Processor may play a role in breast fine-needle aspiration, but further investigation is warranted before it is used as a sole preparatory method.