Normal preoperative calcitonin levels do not always exclude medullary thyroid carcinoma in patients with large palpable thyroid masses

Medullary thyroid carcinoma (MCT) is a sporadic or familial tumor of the pa rafollicular or C-cells that secretes calcitonin. The sporadic form usually presents with a palpable thyroid nodule or cervical adenopathy, by which t ime basal calcitonin levels are almost always elevated. Without special sta ins, fine-needle biopsy may fail to detect MCT. Recently, several investiga tors have recommended routine measurement of serum calcitonin in patients w ith nodular thyroid diseases for the preoperative diagnosis of MCT. A 31-ye ar-old woman had a large palpable MCT with normal calcitonin and carcinoemb ryonic antigen levels before surgery. Fine-needle aspiration (FNA) demonstr ated atypical cells but was not diagnostic of MCT. Pathology revealed a 3 x 4.5 x 2.3 cm MCT. Immunochemical stains showed immunoreactivity for calcit onin and synaptophysin, but no immunoreactivity to thyroglobulin. Postopera tive basal and pentagastrin-stimulated calcitonin levels have remained unde tectable without evidence of recurrent cancer. We have evaluated six other patients with MCT that were palpable. They had preoperative calcitonin leve ls ranging from 322-50,032 pmol/L. This unique case of a woman with a 4.5-c m MCT and normal preoperative calcitonin levels, emphasizes the need for ca reful clinical evaluation and FNA biopsy in managing patients with nodular thyroid disease.