Cell block findings from residual PreservCyt samples in unsatisfactory ThinPrep Paps: no additional benefit

Our objective was to determine whether cell blocks (CB) performed on unsatisfactory ThinPrep Pap Test residual samples rendered additional clinically significant pathologic findings not detected in the original ThinPrep Pap smears. One hundred consecutive ThinPrep Paps categorized as unsatisfactory were selected for this study. The cytologic diagnosis of unsatisfactory was based on lack of cellularity (squamous) or complete obscuring blood or inflammation. Residual PreservCyt samples from these consecutive unsatisfactory ThinPrepPaps were used to prepare a cell block, using the inverted filter technique. One hematoxylin-eosin (H&E)-stained slide was prepared and evaluated. The amount and the cellular changes were noted for all smear constituents and compared with the original slides. The average patient age was 32 +/- 11 yr. The ThinPrepPap was performed as a follow-up on a previous abnormal smear (12%), pregnancy (25%), abnormal bleeding (22%), or previous unsatisfactory ThinPrepPap (5%), or as routine screening (36%). Variable amounts of endocervical cells, endometrial cells, and metaplastic cells, as well as a variable number of squamous epithelial cells, were present in 89%, 9%, 50%, and 35% in the CB method vs. ThinPrep, respectively. Abnormal cellular changes were noted in 15% of patients (9% with LSIL, and 6% with atypia of undetermined significance); 9 patients with squamous dysplasia had a previous abnormal ThinPrep Pap. A follow-up Pap smear and/or cervical biopsy were performed in 10 of the 15 patients with abnormal cytology detected on CB method revealing: LSIL (1 patient), HSIL (1 patient), ASCUS (1 patient), and within normal limits (7 patients). The findings indicate that the preparation of a CB does not contribute significantly. Importantly, no carcinomas or HSILs were identified on CB preparations. Since a large majority of lesions identified were LSILs, a repeat Pap smear in these cases represented a more cost-effective strategy than cell block preparation, although a cell block preparation may be useful in selected cases.