Use of immunohistochemistry in fine needle aspiration of thyroid nodules in patients with a history of malignancy - A report of two cases

BACKGROUND: A history of a nonthyroid malignancy may present a diagnostic d ilemma in the assessment of fine needle aspiration (FNA) of thyroid nodules . One reported series, on patients with prior malignancies and a thyroid no dule, indicated that in 17% of patients, the thyroid nodule represented met astatic malignancy, 6% were classified as primary thyroid cancers, and the remainder were benign or inconclusive lesions. The resolution of this probl em is essential to patient management. CASES: We report two cases in which patients with a history of renal cell c arcinoma presented with a thyroid nodule. The first patient was an 80-year- old female whose Papanicolaou-stained FNA demonstrated clusters of round to polygonal cells with round to ovoid, hyperchromic nuclei and abundant, wis py cytoplasm. The second patient teas a 55-year-old female with clusters an d single cells with round to oval, eccentric nuclei and copious, granular, gray cytoplasm noted on Papanicolaou-stained material. In each case, the di agnosis was inconclusive on initial review of Papanicolaou-stained slides, and immunohistochemical staining was ordered to better characterize the les ions. Tumor cells from case I were positive for cytokeratin cocktail and vi mentin and negative for thyroglobulin, epithelial membrane antigen and calc itonin, suggestive of metastatic renal cell carcinoma. In contrast, the tum or cells from case 2 expressed cytokeratin, thyroglobulin and vimentin, con sistent with a primary thyroid neoplasm. In each case, the cytologic diagno ses were confirmed in the resected specimens. CONCLUSION: Immunohistochemistry is a helpful adjunct in the evaluation of thyroid nodules in patients with a past history of malignancy.