Comparison of ThinPrep and conventional smears in salivary gland fine-needle aspiration biopsies.

BACKGROUND. ThinPrep (TP) cytology for evaluation of nongynecological specimens is being increasingly used. There are few studies comparing TP with conventional smears (CS) in salivary gland (SG) fine-needle aspiration biopsies (FNAB). This study compares diagnostic accuracy and morphology of TP and CS in SG FNABs. METHODS. The authors retrospectively reviewed 98 satisfactory SG FNABs with both TP and CS. All cases had surgical resection. CS and TP slides were assessed for multiple morphological parameters, as well as the ability to make the diagnosis. Chi-square analysis was performed to compare CS and TP. RESULTS. An accurate diagnosis was rendered more commonly with CS compared with TP (57% versus 42%; P=.032), whereas the unsatisfactory rate was greater with TP compared with CS (19% versus 9%; P =.041). The error (4%) and indeterminate (35%) rates for TP were similar to CS. The diagnostic yield was greater for cellular cases, which were more frequent with CS compared with TP, than for cases of low cellularity; the diagnostic yield of cellular TP cases and cellular CS cases was similar. Artifacts (crush, air drying, obscuring blood) were more frequent (12%, 13%, and 27% versus 2%, 0%, and 1%; P <=.006) in CS compared with TP Although fragmentation was greater and nuclear detail was better in TP (P <=.03), cell size was larger in CS (P=.002). A specific diagnosis of pleomorphic adenoma (PA) was more frequently rendered with CS compared with TP (83% versus 63%; P =.045). PA stroma was more abundant, and an epithelial-stromal interface (ESI) was more frequent in CS compared with TP (ESI, 76% versus 38%; P <=.001). CONCLUSIONS. There are morphological differences between TP and CS in SG FNABs, especially with respect to stromal appearance. Although CS appears to be preferable to TP in the diagnosis of PA overall, CS and TP have equivalent diagnostic yield in highly cellular cases. Complementary use of both TP and CS preparations to achieve optimal diagnostic yield is recommended, given the artifacts of some CS and the not infrequent unsatisfactory nature of 1 preparation alone.