The prognostic value of calcitonin immunostaining in medullary carcinoma of the thyroid.

This study was undertaken to evaluate the prognostic value of calcitonin (CT) immunostaining in medullary carcinoma of the thyroid (MCT). Primary tumors and metastases from 44 patients with MCT were stained for CT using the immunoperoxidase method. According to the number of cells stained in the primary tumors, the patients were subdivided into 3 groups. Group A included 9 patients with CT-poor tumors (less than 25% of cells stained), group C consisted of 21 patients with CT-rich tumors (greater than 75% of cells stained), and group B included 14 patients with intermediate tumors (25-75% of cells stained). Group A and B patients presented with more advanced disease and had a higher rate of recurrence than group C patients, but the difference was not statistically significant. The number of cells stained correlated well with survival, which was significantly longer for group C than groups B (P = 0.044) and A (P = 0.001). Group B patients survived longer than did those of group A (P = 0.036). The 5-yr survival rates were 52.7%, 93%, and 100% for groups A, B, and C, respectively. Eighty-three percent of patients with multiple endocrine neoplasia IIa had CT-rich tumors, whereas 78.3% of those with sporadic disease had CT-poor ones (P less than 0.001). CT-rich metastases were compatible with prolonged survival even if they were affecting vital organs, whereas CT-poor metastases were virulent and carried a poor prognosis. Therefore, CT immunostaining is recommended for all patients with MCT, as it can predict the course of the disease. It also can be used as a staging procedure and may help the clinician in making a decision regarding the therapeutic approach.