| A rare thyroid tumor characterized by a malignant neoplasm derived from the calcitonin-secreting parafollicular C-cells of the thyroid and occurring familially, but not as a component of multiple endocrine neoplasia syndromes. The commonly multifocal, bilateral nodules are typically located at the junction of the upper and middle thirds of the thyroid lobes. Clinically, patients may present with diarrhea, flushing, or weight loss caused by excessive secretion of calcitonin by the tumor. In rare cases, the tumor can also cause Cushing syndrome due to ectopic corticotropin production. |
