Thyroid carcinoma with biphasic clinical course and evolution in medullary carcinoma-follicular variant. A case report and an immunocytochemical demonstration of calcitonin and thyroglobulin in the same neoplastic cells.

: The authors present an unusual case of thyroid neoplasia firstly diagnosed as an anaplastic carcinoma with no rise in plasma thyroglobulin (Tg) and treated with total thyroidectomy and radioiodine administration. After 18 months regional lymph node metastases were present with a rise in plasma calcitonin (Ct) (8000-14000 pg/ml); lymphectomy and external radiation were performed and histology revealed a metastasis from thyroid medullary carcinoma. After 3 years, mediastinal and right supraclavicular masses were present with a concomitant rise in plasma calcitonin (from 700 to 3400 pg/ml); all neoplastic lesions showed radioiodine uptake and plasma Tg was 8.9 ng/ml. A biopsy of the supraclavicular region was taken and 131I therapy was attempted, but the patient died after 6 months. Immunocytochemistry of the biopsy revealed the presence of a medullary carcinoma-follicular variant: the neoplastic cells were variably reacting with anti-Ct and anti Tg, and, moreover, the two antigens were sometimes observed in the same cell bodies. The metabolic pattern and the clinical course of this tumour are discussed, and the authors propose that Ct and Tg plasma levels be evaluated and a total body scan (WBS) with radioiodine be performed in all cases of medullary or poorly differentiated thyroid carcinomas.