Fine-needle aspiration cytology of unsuspected metastatic thyroid carcinoma initially presenting in bone: Report of three cases and a review of the literature

We present a series of three cases of unsuspected thyroid carcinoma present ing as bony lesions and initially studied by fine-needle aspiration (FNA). This series consists of two cases of follicular carcinoma and a third case of Hurthle cell carcinoma. FNA was performed on all three lesions. In two o f these cases, a definitive diagnosis of metastatic thyroid carcinoma was m ade based on the FNA material. FNA smears of both follicular carcinomas dis played cohesive clusters of atypical round cells with nuclear overlapping a nd positive immunoperoxidase staining for thyroglobulin. The aspirates of t he Hurthle cell carcinoma were composed of sheets and individually scattere d oval oncocytic cells with prominent nucleoli. All three cases demonstrate d the presence of marginal vacuoles consistent with "flame" cells. To the b est of our knowledge, this is the first series discussing the cytologic fea tures and differential diagnosis of unsuspected thyroid carcinoma initially presenting as metastatic bone lesions. Diagn. Cytopathol. 2000;22:313-318. (C) 2000 Wiley-Liss, Inc.