Immunocytochemistry on the Thinprep® processor

Introduction: For cytologic specimens, the vast majority of immunocytochemical studies (ICC) are performed on non-gynecologic specimens for diagnostic purposes, and they can be performed on unstained or previously stained direct smears. Although the ThinPrep® processor (TPP) has been approved for the preparation of non-gynecologic specimens, there is scant literature describing the utility of ICC methodology on cytology specimens fixed and processed by this method. Materials and Methods: Forty-one fresh specimens were obtained from the surgical gross room and aspirated or scraped to collect cells for thin layer (TL) and direct smears (DS). Specimens included a variety of neoplastic and nonneoplastic samples that were either Papanicolaou (P) stained or unstained (US). One group of US TL slides was subjected to antigen retrieval (AR). Staining was graded semiquantitatively. Each sample acted as its own control. Antibodies (abs) included: CAM5.2, AE1/3, K903, vimentin, MSA, desmin, s-100, HMB45, PSA, PAP, chromogranin, NSE, insulin, synaptophysin, pCEA, mCEA, mCEAD14, LCA, L26, UCHL-1, OPD-4, thyroglobulin, GCDFP, ER/PR, laminin, collagen IV, PLAP, HCG, CD68, HAM56, and MAC387. Results: Semiquantitative staining overall results comparisons: TLP > DSP TLP < DSP TLP = DSP TLUS > DSUS 11/25 (44%) 6/25 (24%) 8/25 (32%) 9/24 (38%) TLUS < DSUS TLUS = DSUS 3/24 (12%) 12/24 (50%) TLP Vs. TLUS TLP > TLUS TLP < TLUS TLP = TLUS 8/41 (20%) 9/41 (22%) 24/41 (58%) There were five false-negative results, 2 with TL and 3 DS, and 1 false-positive TL. Discussion: Immunocytochemistry performed on the ThinPrep® Processor showed equal or greater intensity and distribution of proper staining when compared to direct smears with the following advantages: (1) cleaner background, easier to interpret; (2) less abs required in a smaller area; (3) IPX can be done on Papanicolaou-stained thin layer slides; (4) thin layer slides can be modified for multiple abs tests; (5) additional thin layer slides can be prepared for ICC bases on needs. No significant differences of immunostaining were seen when comparing thin layer Papanicolaou-stained and unstained slides. Antigen retrieval offered no advantage in this study.