Primary hyperparathyroidism (PHPT) is mostly due to a benign parathyroid tumor (99%). Some have parathyroid atypical adenomas, rare tumors with histological features of parathyroid cancer (PC) (fibrous trabeculae, thick fibrous bands, mitotic figures in parenchymal cells), without local invasion or metastasis. We evaluated 20 patients with histological diagnosis of atypical adenomas. Patients were 13 women and seven males (mean age: 55±13 yrs). Nineteen patients had a sporadic PHPT and one a Familial Isolated PHPT (FIHP). At least one of the following symptoms was present in 8 (40%) patients: nephrolithiasis (n=8), clinical fragility fractures (n=1), neuropsychiatric symptoms (n=6). In the remining patients (n=12) PHPT was asymptomatic. Osteoporosis was detected in 8 (40%). Preoperative imaging was positive in 16 (80%) patients. The association with other tumors was recorded: papillary thyroid carcinoma (n=4), adrenal bilateral hyperplasia (n=1), breast cancer (n=1), Mortons neuroma (n=1). Biochemical tests at baseline were: albumin adjusted serum calcium 12.4±0.8 mg/dl, PTH 204 (160277) pg/ml and 25OHD 13.4±7 ng/ml. All patients underwent PTx. The histological diagnosis was of atypical adenoma (mean diameter 24±10.6 mm) with the following features: fibrous trabeculae in two, thick fibrous bands in 13, capsular invasion infiltration in seven and mitotic figures in two. All but one patients were cured after PTx and remained normocalcemic (mean follow-up 5 years). One patient, with apparently sporadic PHPT, had persistent hypercalcemia and he is in follow-up. This study suggests that PHPT due to atypical adenoma is generally asymptomatic at diagnosis, it has a moderate-severe biochemical profile resembling that of PC, it is a sporadic disease and shows a benign prognosis in the majority of cases. We found an association with other tumors, that will be evaluated in further studies.
20 - 23 May 2017
European Society of Endocrinology