Pathological findings of gray-zone papillary thyroid carcinoma

In the 2010 Japanese guidelines for the management of thyroid tumor, patients with papillary thyroid carcinoma excluding those in the low-risk and high-risk groups were classified into the gray-zone risk group, and the committee of the Japanese guidelines left the extent of surgery for this group to the discretion of each surgeon. In this study, we histologically examined extirpated thyroids in 20 patients with gray-zone carcinoma to determine their pathological findings. Intraglandular cancer foci in the affected side were observed in 9 patients and those in the opposite side were identified in 7 of 8 patients who received operations over subtotal thyroidectomy. Vascular invasion was observed in 15 patients in spite of all patients being M0. Lymphatic invasion and lymph node metastases were observed in 6 patients and 9 patients, respectively. These results showed that gray-zone carcinoma had a relatively high incidence of intraglandular cancer focus, vascular invasion and lymph node metastasis.