Recurrent occult medullary thyroid carcinoma detected by MR imaging.

Abstract

Medullary carcinoma of the thyroid originates in the parafollicular or C cells of the thyroid gland. These C cells produce calcitonin, which is a sensitive marker for the presence of tumor. Measurement of plasma calcitonin level is an important tool for early diagnosis and for monitoring the results of treatment [1 , 2]. In patients with medullary carcinoma treated by total thyroidectomy, rising plasma calcitonin levels almost always signify growth of recurrent or residual tumor. In a patient who has a rising level of plasma calcitonin after total thyroidectomy, localization of regional or systemic disease is important for subsequent management. Several methods, including CT scanning [i], sonography [3], 1311-metaiodobenzylguanidine(1311-MIBG) scanning [4], and selective venous catheterization with quantitative calcitonin measurement [5], have been reported as useful in detecting the location of medullary thyroid cancer. We report a patient with rising plasma calcitonin levels whose recurrent tumor was not localized by physical examination, CT scan, or 1311-MIBG scan. MR imaging clearly showed residual tumor in the neck. This experience suggests that MR may be useful in localizing residual or recurrent disease in patients being monitored for medullary carcinoma of the thyroid.