ThinPrep vs. conventional smears in fine-needle aspirations of sarcomas: A morphological and immunocytochemical study

Very limited data exist describing the characteristics of sarcomas sampled by fine-needle aspiration (FNA) and processed by the ThinPrep (TP) method. We compared the cytopathological and immunocytochemical features of sarcoma aspirates prepared using both the conventional and TP method. We reviewed 70 sarcoma FNAs. Samples were first used to prepare conventional smears and the remainder of the specimen was rinsed in Cytolyt. The average number of slides examined per case was two for the TP method and five for the conventional technique. Immunocytochemistry for different markers was performed in a subset of cases. Sixty-five cases were positive for sarcoma both by conventional and TP methods. Five cases were positive by one method only. Cellularity was higher on conventional slides. In terms of cytoarchitecture, TP slides revealed fewer thick clusters, more single cells that were more evenly distributed, and sometimes distortion of expected cellular arrangements and architectural patterns. Cytomorphological and nuclear details were better preserved on TP slides. The background of TP slides revealed a reduction of blood but also some loss of necrosis and characteristic background tumor features. Immunocytochemical staining revealed superior results on TP slides. TP and conventional slides showed good correlation. TPs were excellent for immunocytochemistry and represent an alternative to conventional smears when expertise in slide preparation is not available. However, TPs may require additional experience in the interpretation of sarcomas, mainly related to the loss of tumor-specific background features. They are useful as an adjuvant to conventional smears in sarcoma diagnoses, particularly when special studies are needed. Diagn. Cytopathol. 1999;21:351-354.