Hypercalcitoninemia and thyroid nodules: when cytology (still) matters

Medullary thyroid carcinoma (MTC) can assume various cytomorphological and architectural forms, mimicking other thyroid and extra-thyroid tumors and rendering the cytological and histological diagnosis challenging. Consequently, measurement of calcitonin (CT) levels is generally considered to be more accurate than cytology in diagnosing MTC. Here, we report on a patient with a multinodular goiter and significantly elevated basal CT levels; based on cytology examination and CT immunocytostains, neither MTC nor C-cell hyperplasia was detected upon final histopathological examination. CT testing has a high false-positive rate and low positive predictive value for detecting clinically relevant MTC. Judicious integration of cytological examination with immunocytochemical stains (when needed) may be useful for selecting the most appropriate therapy and avoiding overtreatment (i.e., central neck lymph node dissection in the present case). This case demonstrates that cytological examination with ancillary techniques is still valuable in patients with thyroid nodules and suspicious MTC.