Endocrine Abstracts

Introduction: Primary hyperparathyrodism is due to benign parathyroid adenomas in more than 90% and parathyroid cancer (PC) in less than 1% of cases. There are no definite clinical criteria differentiating PCs and adenomas. Another subtype, parathyroid neoplasm of uncertain potential is also referred as atypical parathyroid adenoma (APA) and share a few histopathologic features common to cancers.

Case: A 47 year old female patient was consulted due to hypercalcemia (total calcium 23.3 mg/dl) and admitted to endocrinology clinic. She was complaining of nausea, vomiting, vague abdominal and skeletal pain, fatigue, and muscle weaknees for 1 month. Her past medical history was nonsignificant. She denied urolithiasis and fracture due to osteoporosis. On physical examination oral mucosa was dry, and thyroid palpable on left side. We suspected PC or another malignancy related hypercalcemia due to severe hypercalcemia. Saline, furosemide, and zoledronate were infused along with subcutaneous calcitonin. Laboratory studies revealed high parathyroid hormone (PTH) (3134 pg/ml), hypercalciuria (381 mg/day), and vitamin D deficiency (8.2 ng/ml). T score and Z score of femur neck and lumbar spine were −3.5 on DEXA study. 4 days after admission calcium level was normalized. Impaired phosphorus, creatinine, and potassium levels improved with therapy. Neck ultrasound revealed a hypoechoic nodule 32.7×24.0 mm in size without suspicious lymph nodes. Tc-MIBI scan revealed increased uptake. A lobulated heterogenous mass 32×28 mm in size in close proximity to oesophagus was observed on contrast enhanced thorax-neck CT series. Invasion to neighbouring tissues and pathologic lymphadenopathies were absent. Histopathologic evaluation yielded an encapsulated parathyroid adenoma measuring 40×30×20 mm in size and equivocal areas of capsular invasion. Stains for PTH, Cyclin D1, and p53 were positive and negative for TTF-1 (−). Kİ67 was %15. Neither HRPT2 gene mutation analysis nor immunostain for parafibromin were available. After successful operation, PTH dropped to 82.6 pg/ml and a nadir of 19.4 pg/ml. While minimum calcium level was 7.8 mg/dl on 5th day of the operation, ALP reached 555 U/l at maximum. She was eucalcemic at the last time she was seen.

Conclusion: There is no single histologic feature pathognomonic of PC and APAs. APAs may present with severe hypercalcemia and very high levels of PTH similar to parathyroid cancers. The definition vascular invasion is also important. APAs must be kept in mind in differential diagnosis of primary hyperparathyroidism.