Recurrent hyperparathyroidism from benign neoplastic seeding: a review with recommendations for management

Benign neoplastic seeding represents a rare cause of hyperparathyroidism found at parathyroid reoperations. It consists of pathologically benign neoplastic parathyroid tissue scattered throughout a previous parathyroid surgical site. We describe a case of recurrent and then persistent hyperparathyroidism occurring in a patient during an 18-year period. The patient's third operation showed nonmalignant parathyroid tissue throughout the right neck bed, which necessitated extensive parathyroid and fibrofatty tissue dissection and a thyroidectomy. This unexpected finding of extensive parathyroid seeding has only been described in detail in ten other patients in the past. A review of these 11 patients shows several features: initial operations were for large parathyroid tumors or cysts in six patients; rupture and spillage of contents occurred in six; and initial hypercalcemia was severe in several patients, perhaps indicating inherently more aggressive tumors. The appearance of benign neoplastic seeding resembled parathyroid carcinoma in its local invasiveness. Therefore the presence of anaplasia, mitoses, capsular invasion, and cellular spindling must be relied on as distinguishing factors. When confronted with this presentation, we recommend removal of all nodal bearing, thyroid, and fibrofatty tissue from the level of the thyroid cartilage to the superior mediastinum and a thyroidectomy if necessary.