Macrofollicular variant of papillary thyroid carcinoma: its clinicopathological features and long-term prognosis.

Macrofollicular variant is a rare entity of papillary carcinoma. We previously demonstrated that this variant accounts for 0.3% of papillary carcinoma in Japan. In this study, we investigated the biological characteristics of 5 cases of macrofollicular variant. We reviewed the diagnosis and clinical course of 5 patients with macrofollicular variant. On preoperative ultrasonographic study, 2 cases were diagnosed as having benign nodule and the remaining 3 suspected of having papillary carcinoma, although they lacked typical ultrasonographic findings of papillary carcinoma. Cytological findings suggested papillary carcinoma for 3 cases and the remaining 2 were diagnosed as indeterminate. Based on both examinations, 4 of 5 patients were diagnosed as having or suspected of having papillary carcinoma. All patients underwent thyroidectomy with lymph node dissection. Three patients underwent central node dissection and the remaining 2 underwent modified radical neck dissection. None of these patients showed clinically apparent node metastasis or massive extrathyroid extension, although 3 of these patients had latent node metastasis confirmed by pathological examination. All patients survived with no evidence of carcinoma recurrence during follow-up (145-235 months). It is therefore suggested that patients with macrofollicular variant can be diagnosed as having or suspected of having papillary carcinoma if ultrasonographic and cytological examinations are appropriately performed and show an excellent prognosis possibly because this variant lacks the aggressive characteristics of papillary carcinoma.