Aggressive clinical course of medullary thyroid microcarcinoma

Abstract

Medullary thyroid carcinoma is a form of neuroendocrine tumor that arises from parafollicular C cells which produce calcitonin. In addition to calcitonin, these cells produce smaller amounts of other peptides, including carcinoembryonic antigen (CEA), which is used as a nonspecific tumor marker in the follow-up of patients with this tumor. MTC is a rare thyroid tumor and occurs three times more often in women than in men. It can occur in two forms, sporadic (80%) and familial form (20%). The familial form can occur alone or in association with other endocrine tumors within MEN 2A and MEN 2B syndromes. The sporadic form most often occurs in the fifth and sixth decades of life. The familial form is inherited autosomally dominantly, most often based on a mutation in the RET protooncogene located on chromosome 10. C-cell hyperplasia is considered to be a premalignant lesion, which precedes medullary carcinoma. Medullary carcinoma metastasizes very early. We presented a patient with a sporadic form of MTC which appeared at a typical age. Initial values of both baseline and stimulated calcitonin were not in the range for suspected MCT, but due to persistent increases in calcitonin, with elevated baseline (63 pg / mL) and higher stimulated calcitonin (96 pg / mL), the patient was referred for surgical treatment. Due to the strong correlation of calcitonin values with tumor size, the initial calcitonin values were expected to be low because the tumor was 3 mm in size. The histopathological diagnosis was C-cell hyperplasia. However, due to the fact that nodular C-cell hyperplasia is histopathologically difficult to distinguish from medullary microcarcinoma, based on the persistent increase in calcitonin levels, the patient was likely to already have metastatic disease at the time of thyroidectomy. Definitive diagnosis was made by liver biopsy. Therapy with tyrosine kinase inhibitors was introduced, and calcitonin levels strarted to decrea, but there is an increase in carcinoembryonic antigen, which is a poor prognostic parameter.