UTILITY OF THIN-LAYER PREPARATIONS IN THYROID FINE-NEEDLE ASPIRATION - DIAGNOSTIC-ACCURACY, CYTOMORPHOLOGY, AND OPTIMAL SAMPLE PREPARATION

BACKGROUND. The efficacy of preparing thyroid fine-needle aspirations (FNAs) as thin-layer slides has not been evaluated extensively. METHOD S, To evaluate the efficacy of thin-layer cytology, the authors examin ed thyroid FNAs from 135 unselected palpable lesions that were aspirat ed using uniform procedures and prepared as air-dried, Diff-Quik(R)-st ained direct smears (DS) and Papanicolaou-stained thin-layer slides (T L). Diagnoses rendered independently on masked slides from each thyroi d nodule were compared with the reported final cytologic or histologic diagnoses based on all available pathologic material. Slides were ana lyzed for diagnostically important cytologic features and the optimal number of TL slides per sample was assessed. RESULTS, TL diagnoses agr eed with final diagnoses in 85% of cases compared with 96% for DS. ALL 11 neoplasms were recognized in both preparations. A final diagno sis of chronic lymphocytic thyroiditis (CLT) was missed in 10 of 26 TL (3 9%) compared with 2 of 26 DS (8%) (P = 0.013, McNemar's test). Cytolog ic features appreciated less often in TL than DS (McNemar's test) incl uded diffuse colloid, spherules, tissue fragments, and lymphocytes. Mu ltinucleated giant cells were identified more often in TL than DS. Two TL slides were sufficient for diagnosis in 83% of cases. CONCLUSIONS, The diagnostic accuracy of TL was 85% compared with 96% for DS. CLT w as diagnosed accurately in 62% of TL compared with 92% of DS. Cytologi c features in TL and DS may differ. Preparation of only two TL slides is adequate for definitive diagnosis in most cases. (C) 1998 American Cancer Society.