Background: In some instances, thyroid cancer may be diagnosed with histological examination after resection of putative or suspected benign nodule. In these cases, completion thyroidectomy followed by radioiodine ablation is usually recommended to prevent recurrence. If small intrathyroidal cancer is found, completion thyroidectomy may not be performed. Many patients have separate cancers in the contralateral lobe and in these cases completion thyroidectomy is essential even though primary tumour is small and limited within thyroid.
Objective: We analysed the frequency of malignant lesions in the contralateral lobe after completion thyroidectomy and assessed the predictive factors that may anticipate the presence of malignant lesion that may necessitate completion thyroidectomy.
Patients: Between 1995 and 2001, 243 patients were operated under the cytological diagnosis of follicular neoplasm. A total of 214 of them underwent lobectomy and isthmectomy and 81 turned out to have malignant disease in the resected lobe and they underwent completion thyroidectomy within a week to 6 months after the permanent section diagnosis of cancer. Their mean age was 40.7 +/- 12.1 years (range 14-71 years).
Results: After initial surgery, 53 patients had follicular carcinoma, 24 papillary carcinoma, one Hürthle cell carcinoma, one medullary, one insular and one anaplastic carcinoma. Mean tumour size was 4.1 +/- 2.6 cm (range 0.9-11 cm). After completion thyroidectomy, factors predicting the presence of cancer in the contralateral lobe were assessed according to clinical parameters and pathologic findings in ipsilateral lobe. First surgery revealed cancer multifocality in 34 cases, perithyroidal tumour extension in six and regional lymph node metastases in three. After completion thyroidectomy, 29 of the 81 patients revealed additional cancer in the contralateral lobe. Age, sex, size or pathologic type of the primary tumour was not associated with the presence of additional tumour in the contralateral lobe. Cancer multifocality in the ipsilateral lobe was the only significant variable to predict the presence of additional cancer in the contralateral lobe (relative risk = 6.03, confidence interval 2.23-16.35). Coexistence of benign nodule in ipsilateral lobe was not associated with increased cancer risk in the contralateral lobe.
Conclusions: When diagnosed as thyroid cancer after unilateral surgery, the only predictive factor for the presence of additional contralateral cancer was multifocality of cancer in the ipsilateral lobe. We suggest that completion thyroidectomy is mandatory if multifocal cancers are found in the resected lobe, even though the cancers are very small and limited within the thyroid.