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.

The detection of early, well-differentiated breast carcinoma is increasing because of mammographic screening. Because fine-needle aspiration cytology is often used as an adjunctive diagnostic tool with mammography, the authors defined the cytologic criteria for the diagnosis of this early breast carcinoma. Aspirates from 24 cases of biopsy-confirmed tubular carcinoma were studied. The majority of these carcinomas were detected by mammography and were nonpalpable masses. Mammographically, the lesions were .3-1.5 cm and were often described as ill-defined, spiculated densities. The cytologic diagnoses in these 24 cases were as follows: negative (4), fibrocystic changes (1), atypia (12), malignant (3), and fibroadenomas (4), (including 2 fibroadenomata with atypia and 1 suspicious for carcinoma). The aspiration cytology in all cases were reviewed, and the following characteristics were found in the 20 adequate smears: mild to moderate atypia, increased cellularity, angular epithelial clusters, and single epithelial cells ranging from few to numerous. Myoepithelial cells were prominent in 7 of 20 smears. The authors compared these features with aspiration cytology of 10 fibroadenomas, as this was a frequently suggested diagnosis. The fibroadenomas showed no significant atypia, minimal angular epithelial clusters, and rare single epithelial cells. Myoepithelial cells were prominent in all fibroadenomas. The authors concluded that the presence of angular epithelial groups and single epithelial cells, along with nuclear atypia, should warrant consideration of the diagnosis of tubular carcinoma.

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Epithelial hyperplasia, a component of proliferative breast disease (PBD), is a known risk factor for the development of breast carcinoma. To determine if criteria established for tissue biopsy could be used to more precisely define cytologic criteria for diagnosis of PBD, 37 breast fine-needle aspirates with biopsy diagnoses of PBD were studied. In cases with adequate cellularity, the following findings were consistently observed: (1) three-dimensional cell clusters with outlying myoepithelial cells, swirling intralumenal masses and peripheral, slit-like, irregular sublumens (65% of cases); (2) convoluted sheets of ductal epithelium with outlying myoepithelial cells and bulbous projections tethered to the ductal lining (29%); and (3) a background of discohesive small frayed groups of ductal cells (32%). Of the 15 cases that did not meet these criteria, most were paucicellular (87%), which suggested sampling error. Other cytologic features that were observed included: moderately increased cellularity (20 cases), moderate-to-marked nuclear overlap (14 cases), minimal nuclear atypia, and few single epithelial cells. Fifteen cases of confirmed ductal carcinoma in situ were studied for comparison. In these cases, cellularity, nuclear overlap, and atypia were increased, but swirling intralumenal masses, prominent myoepithelial cells and slit-like lumens were absent. In conclusion, the features of PBD established for tissue biopsy can be applied to cytologic specimens, and may provide useful clues to the diagnosis of epithelial hyperplasia in breast fine-needle aspiration specimens.

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