Parathyroid involvement in thyroid cancer: an unforeseen event

BACKGROUND Parathyroid metastatic disease from thyroid cancer has not been studied extensively, mainly due to the need for parathyroid preservation during thyroid surgery. METHODS We reviewed files from 1,770 patients with thyroid cancer followed up in our department and 10 patients with parathyroid metastases (0.5%) were identified. Patient and tumor characteristics were recorded. RESULTS Six out of ten patients had metastases from papillary thyroid cancer, three from follicular thyroid cancer and one from anaplastic thyroid cancer. In nine patients parathyroid infiltration from thyroid cancer was found in direct contact with the thyroid cancer, and in one patient metastatic foci were observed not in continuity with the thyroid cancer. CONCLUSIONS Parathyroid involvement, although infrequent, may occur in thyroid cancer independently of patient age and tumor size. The clinical significance of such event is not clear. The influence on disease outcome remains to be elucidated.