Cytologic features of small-cell carcinoma on ThinPrep

The use of ThinPrep (TP) technology for fine-needle aspiration (FNA) cytology has become widely accepted. However, some literature suggests that small-cell carcinoma may present a diagnostic pitfall due to morphologic alterations. In this study, we retrospectively compared 14 FNA of small-cell carcinoma prepared using TP with corresponding conventional smears (CS). We also examined the TP appearance of 23 other small round-cell lesions in order to determine if differential diagnostic features were preserved. TP and CS were evaluated semiquantitatively for background, architecture, chromatin quality, nuclear molding, nuclear smearing, nucleolar prominence, amount of cytoplasm, nuclear size, and single-cell necrosis. The data were analyzed using the McNemar chi(2) test. TP slides of small-cell carcinoma showed a cleaner background than CS (P < 0.005). Although some degree of nuclear molding was preserved, it was decreased in amount (P < 0.025) and subtler in quality. Similarly, nuclear smearing was present but decreased in amount (P < 0.05), and less prominent qualitatively. The amount of discernible cytoplasm was greater on TP (P < 0.005). No significant differences were found for any of the other parameters studied. The presence of nuclear molding was the single most useful feature in differentiating small-cell carcinoma from other small round-cell tumors on TP. Small-cell carcinoma may be diagnosed with confidence by FNA using TP. However, pathologists should be aware of certain morphologic alterations in order to avoid diagnostic pitfalls.