Endocrine Abstracts

Introduction: The coexistence of two types of tumors of different origins in the same thyroid is a rare phenomenon. Its etiopathogenesis remains unknown. We report the case of a mixed papillary and medullary carcinoma of the thyroid revealed by a compressive goiter.

Case report: A 70-year old woman with a history of right lobo-isthmusectomy for a toxic solitary adenoma, presented 30 years later with a chief complaint of a cervical mass accompanied by difficulty in swallowing. Her family history was free of any endocrine or non-endocrine malignant tumors. On physical examination, she had a left thyroid nodule of 4 cm in the greatest dimension without palpable cervical lymph nodes. Laboratory tests indicated hyperthyroidism with a decreased TSH of 0.002 μUI/ml and an increased free T4 of 26.6pmol/l. Thyroid scintigraphy showed a toxic multiheteronodular goiter. Cervico-thoracic CT scan showed an intrathoracic goiter exerting a mass effect on the trachea and the esophagus. The serum calcitonin assay was not performed preoperatively. The patient underwent a left thyroid lobectomy without lymph node dissection. Permanent histopathologic analysis revealed mixed papillary and medullary thyroid carcinoma in a multinodular adenomatous goiter. The immunohistochemical study confirms the histopathological examination by showing a calcitonin and a thyroglobulin staining. The patient was planned for a cervical lymph node dissection followed by a radioiodine therapy.

Conclusion: The simultaneous occurrence of medullary and papillary thyroid cancer is the result of a simple coincidence due to the high frequency of papillary micro carcinomas of the thyroid. This case illustrates the importance of the thyrocalcitonin assay in presence of any thyroid nodule.