Usefulness of paraffin embedding as complementary technic in the diagnosis of thyroid aspirates

PURPOSE: To compare the diagnostic value of conventional direct cytologic smears and paraffin embedding in the preparation of samples obtained by fine needle aspiration (FNA) biopsy. METHODS: Direct smears and paraffin embedding preparations were examined from 100 thyroid lesions. In 9 cases, the FNA smears and paraffin embedding blocks were, in addition, compared with surgical thyroid specimens. RESULTS: The FNA samples were adequate for diagnosis in the great majority of cases (93/100). In 72 aspirates, both smears and paraffin embedding preparations were adequate. In 17 cases only he latter preparations and in 4 specimens only the smears were considered adequate. When both smears and paraffin blocks were available (72 aspirates), there was diagnostic agreement in 63 cases. Overall the diagnostic percentage of FNA/paraffin-block preparations was 95.7% and of FNA/conventional smears was 81.7%. Statistical analysis demonstrated that paraffin blocks increased the diagnostic accuracy of thyroid FNA (p < 0.01). CONCLUSION: Our data point out to the value of complementing conventional FNA smears with paraffin embedding preparations for the diagnosis of thyroid lesions.