Cytologic diagnosis of recurrent medullary thyroid carcinoma with oncocytic change twenty-one years post-thyroidectomy: case report and review of the literature.

A 66-year-old woman presented 21 years prior with diarrhea and elevated serum calcitonin levels. The left lobe of the thyroid was aspirated but specimen was unsatisfactory. Nevertheless, based on the radiological and clinical impressions, the patient underwent total thyroidectomy and the histologic examination established the diagnosis of medullary thyroid carcinoma (MTC). Approximately 5 years later, the patient had a recurrence of the disease and underwent a neck lymph node dissection, which showed metastatic MTC in a lymph node. Sixteen years later, the patient presented with left neck mass detected by ultrasound in the area of thyroid bed. Fine needle aspiration (FNA) of this area was performed and the FNA diagnosis was consistent with oncocytic variant of MTC. This case illustrates a first report of this uncommon variant of MTC diagnosed by FNA cytology of the thyroid bed.