Endocrine Abstracts

Introduction: Atypical parathyroid adenoma (APA) is a difficultly diagnosed tumor, including some histological features of parathyroid carcinoma (PC). In literature, no definite criteria are considered to be present to distinguish preoperatively APA from PC. It is difficult to distinguish APA and PC intraoperatively. Our report, a case applying with high levels of calcium (Ca) and intact parathyroid hormone (iPTH) and diagnosed with APA was presented.

Case: A 65-year-old woman applied to our clinic with arthralgia, myalgia and fatigue. She had severe hypercalcemia (serum Ca 17.2 mg/dl), hypophosphatemia (serum phosphate 1.9 mg/dl) in conjunction with an elevated iPTH level of 879 pg/ml. There was not a lesion consistent with parathyroid adenoma in neck ultrasonography. Tc-99m sestamibi scintigraphy and neck magnetic resonance imagination scans revealed a suspicious lesion that can be a parathyroid adenoma at the posterior region of left thyroid lobe. I.v. hydration and diuretic treatment were given to the patient. Six sessions of hemodialysis were performed. Parathyroidectomy guided by intraoperative gamma probe was performed, and a 3.5×3×2 cm sized parathyroid adenoma was excised. Histopathologically, well-circumscribed parathyroid cell proliferation was seen with solid growth pattern. Round to oval shaped proliferative cells were surrounded by thick fibrous capsule and seperated by dense fibrotic bands. No marked pleomorphism and mitotic figure was present. Ki-67 proliferation index was <1%, and no vessel invasion, complete capsule invasion and invasion to the adjacent structures were observed. In an area, parathyroid cell proliferation became invaded into the capsule, no complete invasion of the capsule was observed. Findings were considered to be related to APA.

Conclusion: No strict clinical and histological criteria are present to distinguish PC from APA. The existence of local recurrence or metastatic disorder is the single and reliable characteristic in distinguishing between benign and malignant parathyroid disorders.