Endocrine Abstracts

Tc-99m sestamibi (MIBI) imaging is able to localize parathyroid adenomas/carcinomas in patients with primary hyperparathyroidism. Brown tumours are one of the skeletal manifestations of long standing hyperparathyroidism and its incidence has been reported to be 3%. Radiological features of these tumors may mimic bone metastasis. There are only a few reports showing brown tumours uptake in the whole-body Tc-sestamibi scan.

We report a 72-year-old female with a previous history of right nephrectomy for renal lithiasis at age 49 and a left clavicle mass fracture. A neck and thoracic computed tomography (CT) scan revealed multiple lytic lesions of the skeleton (including in the left clavicle) and a pathological mandibular fracture, suggesting metastatic lesions.

¹⁸F-FDG PET scan showed multiple skeletal hypermetabolic lesions and a hypermetabolic nodule close to left lower pole of the thyroid gland. The biopsy of the lesion in the left clavicle revealed histiocytic proliferation with multinucleated osteoclast-type giant cells compatible with a brown tumor. Laboratory data showed an elevated serum calcium of 12.8 mg/dl (8.4–10.2), alkaline phosphatase of 264 UI/l (9–36), and parathyroid hormone of 1056 pg/ml (12–65).

Tc-99m sestamibi scintigraphy showed an uptake in the inferior left pole of the thyroid and in multiple bone lesions. The patient underwent a left inferior parathyroidectomy. Histology revealed a 20 mm parathyroid adenoma.

In this patient with a long standing hyperparathyroidism the intense uptake of brown tumors in both ¹⁸F-FDG PET scan and MIBI can mimic a parathyroid carcinoma with bone metastases.