A peculiar case of mixed medullary-papillary thyroid carcinoma [Un raro caso di tumore misto midollare-papillare della tiroide]

Mixed medullary-follicular or papillary carcinomas are seldom found in the thyroid gland. The first one is defined by the WHO classification as a tumour showing both morphological features of medullary and follicular carcinoma with immunoreactive calcitonin and thyroglobulin. The second one is not enough listed in the above-mentioned classification and reports about it are still few. In the reported case, at first, multiple liver metastases were identified. Histological examination showed to be metastases of a papillary carcinoma. The patient subsequently underwent a total thyroidectomy. In the right lobe of the gland a tumour which exhibited features of both medullary and papillary carcinoma and both calcitonin and thyroglobulin immunoreactivity was found. The immunohistochemical examination of the liver metastases revealed the same immunohistochemical findings of the primary thyroid tumour, thus further confirming the diagnosis of mixed medullary-papillary carcinoma of the thyroid gland. The patient was submitted to a radioiodine treatment without success. Subsequent somatostatin analogue treatment induced a remarkable reduction of calcitonin sermn level and US liver metastases disappearance. The recognition of the rare mixed medullaryfollicular or papillary thyroid carcinoma suggests hypotheses on its histogenesis and C cells derivation. Moreover, according to some authors, this mixed tumour might constitute a new clinicopathologic entity, different from the conventional medullary one, with a specific epidemiology, clinical course and new treatment resources.