Parathyroid carcinoma and atypical parathyroid tumor: analysis of an Italian database.

Objective: Atypical parathyroid tumor (aPT) and parathyroid carcinoma (PC) are extremely rare parathyroid neoplasms, accounting together for <2% of all parathyroid tumors. They often present an overlapping clinical phenotype, sharing clinical, biochemical, and some histological features. They are distinguished only by the presence of local invasion, and lymph nodes or distant metastasis, which are all absent in aPTs. To date, only few studies have compared clinical presentation and features between aPTs and PCs. Our purpose was to conduct a retrospective study on a multicenter Italian database of aPT and PC patients.

Design and methods: We comparatively analyzed main features of aPT (n = 57) and PC (n = 74) patients collected at 15 major endocrinology and endocrine surgery centers in Italy.

Results and conclusions: Atypical parathyroid tumors and PCs showed no significant differences in many clinical features and presented similar values of elevated parathyroid hormone and total serum calcium. Renal complications, namely nephrolithiasis and nephrocalcinosis, appeared to be more common in PC, with a significantly higher rate of renal colic, regardless of total serum calcium levels and 24-h calciuria. Parathyroid carcinomas showed significantly higher postoperative disease persistence and recurrence rates, presumably due to an uncomplete resection of the primary tumor in 23.5% of cases and/or presence of unremoved active metastasis, but they had similar disease-free mean time after surgery than aPT. To deepen the study of malignant parathyroid tumors, the institution of a novel Italian retro-prospective multicenter registry of aPTs and PCs is currently ongoing, and a dedicated PC European registry has been recently activated.