Endocrine Abstracts

JOINT3211

Atypical parathyroid adenomas are rare and difficult to diagnose, since their histopathological features overlap with both benign parathyroid adenomas and parathyroid carcinoma. These tumors lack definitive criteria for malignancy, but exhibit worrisome histologic findings such as: increased mitotic activity, trabecular growth patterns and fibrous bands. Clinically, these tumors cause signs and symptoms of primary hyperparathyroidism and hypercalcemia; while imaging modalities, including neck ultrasound, Sestamibi scintigraphy, can identify them. However, definitive diagnosis requires histopathological assessment. We report the case of a 74 year old male, with a history of prostate cancer, who was undergoing routine follow up imaging when a CT scan incidentally identified a lesion posterior to the left thyroid lobe; the scan also revealed multiple pelvic and spinal osteolytic bone metastases, the largest measuring 40x16 mm. Of note, the patient was completely asymptomatic. Endocrinological assessment revealed normal thyroid function, hypercalcemia(Ca=13,3 mg/dl), hyperparathyroidism(1741 pg/ml), low-normal vitamin D levels (20,59 ng/ml) and hypercalciuria (367,2 mg/24h). Neck ultrasound showed a well defined, hypoechoic, highly vascularized mass(3,22x4,9x2,86cm) posterior to the left thyroid lobe, raising suspicion of a parathyroid lesion. BMD-DXA revealed severe osteoporosis in the distal forearm(T score= 5,9) and decreased bone mineral density in the lumbar spine and femoral neck. Hypercalcemia persisted despite intravenous and oral hydration, so intravenous ibandronic acid was administered. A sestamibi thyroid and parathyroid scintigraphy confirmed a large hyperfunctioning parathyroid lesion on the left side, along with a smaller hyperfunctioning inferior right parathyroid lesion and a suspicious thyroid nodule in the lower two-thirds of the left lobe. Additionally, a bone scan identified suspicious bone lesions in the skull as well as the axial and appendicular skeleton. One month later, the patient underwent parathyroidectomy and thyroidectomy, and the histopathological report confirmed an atypical parathyroid adenoma. A bone biopsy was recommended, but has not yet been performed. This case highlights the diagnostic challenge of hypercalcemia in a patient with a history of malignancy. Although the presence of osteolytic bone lesions initially suggested metastatic prostate cancer, distinguishing between malignancy and parathyroid bone disease proved more difficult than expected. This distinction is crucial, since parathyroid bone disease may improve postoperatively, while metastatic disease would persist or progress. Close follow-up and monitoring are essential to reach a correct diagnosis and ensure patient’s well-being in the postoperative period.