Parathyroid invasion, nodal recurrence, and lung metastasis by papillary carcinoma of the thyroid.

AIMS Parathyroid invasion by papillary thyroid carcinoma (PTC) is found in a small proportion of surgical specimens, but the clinicopathological relevance of this phenomenon is not well understood. This study investigated the possible prognostic relevance of parathyroid invasion in PTC. METHOD Parathyroid involvement was seen in 14 patients with PTC, and the clinicopathological characteristics and follow up data of these patients were analysed and compared with 164 patients without parathyroid involvement, in whom histological parathyroid examination had been undertaken, and 177 other patients without parathyroid examination (341 patients without parathyroid involvement in total). RESULTS Parathyroid invasion was found in older patients and there were more male patients in this group than in those without parathyroid invasion. These patients had more extrathyroid extension and were frequently in an advanced stage of disease. Lung metastasis was seen in two of the 14 patients, which was significantly more than that seen in control cases. Moreover, male patients with parathyroid invasion and those who were older than 55 years had reduced disease free survival compared with those without parathyroid invasion. CONCLUSION Parathyroid invasion seen in thyroid carcinoma may be an important histological feature indicating a greater chance of nodal recurrence and lung metastasis.