ACTA ENDOCRINOLOGICA (BUC)

Medullary thyroid carcinoma (MTC) arising from aberrant tissue is almost unknown. Our aim is to report our first case.\r\nObservation. A woman, aged 46, was operated on for multinodular goiter with lateral mass considered as a metastasis. Thyroid surgery was well supported. The surgeon discovered a median thyroid which seemed normal, and a lateral mass totally separated from the thyroid. The pathologist who did very thin slices of the whole thyroid excluded the malignancy, but in the lateral tissue, he discovered a typical MTC with positivity to thyrocalcitonin (TCT), chromogranine A, and thyroid transforming factor1 antibodies. That lateral tissue did not contain any thyroid or lymphoid cells. The tumoral tissue was sent to another\r\npathologist who confirmed the diagnosis. In post operative period TCT was normal (mean value=4.5pg/mL, N<13), but urinary metanephrines were slightly increased (1.32\r\nmg/24h, N=1). Radiological explorations (except MIBG scintigraphy not done for low socioeconomic conditions) failed to show any pheochromocytoma. One year later that one was found by CT scan, and our patient was classified as multiple endocrine neoplasm type 2A. Laparoscopic surgery\r\ndone under thiopental and curare was uneventful, histological exam confirmed the pheochromocytoma. Genetic screening for RET proto-oncogene was negative arguing\r\nfor a sporadic case. Conclusion. MTC located in\r\naccessory thyroid is a scientific curiosity which can be mistaken with a lymph node metastasis. In our case a meticulous exam of the median thyroid and the lack of thyroid and lymph cells in the lateral mass were\r\nagainst the metastasis.