ThinPrep (R) vs. conventional smear cytologic preparations in analyzing fine-needle aspiration specimens from palpable breast masses

Limited data exist concerning the cellular features of the Thin-Prep(R) (Cy tyc Corp., Boxborough, MA) technique in the analysis of breast fine-needle aspiration specimens, Therefore, we analyzed a series of 75 surgically exci sed palpable breast masses and compared ThinPrep and conventional smear fin e-needle aspiration preparations. Each mass was aspirated twice. The first sample was used for two alcohol-fixed conventional swears, and the second s ample was rinsed into CytoLyt (Cytyc Corp., Boxborough, MA) solution for pr ocessing into a ThinPrep slide. The paired slides were separated and indepe ndently analyzed for adequacy, overall cellularity, single epithelial cells (absent, rare, moderate, or numerous), epithelial ni architecture (sheets or three-dimensional clusters), myoepithelial cells and stripped bipolar nu clei (present or absent), and nuclear detail (poor, satisfactory, or excell ent). Each sample was classified as negative, negative consistent with fibr oadenoma, atypical favoring benign, atypical favoring malignant, or positiv e for malignant cells. The 75 breast masses included 32 carcinomas and 43 b enign lesions. Four conventional smears and one ThinPrep were unsatisfactor y. Significantly more conventional smears were limited by drying artifact ( 9 vs. 0). ThinPrep aspirates of carcinomas had better nuclear detail (P = 0 .03) and greater cellularity (P = 0.05). ThinPrep aspirates of benign masse s had greater epithelial cellularity (P = 0.007) and better nuclear derail (P < 0.001), and more specimens had myoepithelial cells (P = 0.007). The Th inPrep interpretation classified 29 of 32 carcinomas (91%) as positive and three as atypical Savoring malignant (sensitivity = 100%). The conventional smear interpretation classified 28 of 31 carcinomas (90%) as positive and three as atypical favoring malignant (sensitivity = 100%). The ThinPrep int erpretation classified 42 benign lesions as negative (23 cases), negative c onsistent with fibroadenoma (8 cases), atypical favoring benign (10 cases), and atypical favoring malignant (1 case) (specificity = 74%). The conventi onal smear interpretation classified 40 benign lesions as negative (25 case s), negative consistent with fibroadenoma (12 cases), and atypical favoring benign (3 cases) (specificity = 93%). ThinPrep was less specific, but the difference was not statistically significant (P = 0.065). In summary ThinPr ep aspirates had greater cellularity and better nuclear detail than convent ional smears, and were just as sensitive in identifying the carcinomas. The difference in specificity between the two techniques was not statistically significant (P = 0.065). Diagn. Cytopathol. 1999;21:137-141. (C) 1999 Wile y-Liss, Inc.