SUN-506 An Interesting Case Of Low-Grade Parathyroid Carcinoma

Abstract

Background: Parathyroid Carcinoma (PC) is a rare form of malignancy and accounts for < 1% of cases of primary Hyperparathyroidism (PHT). It is challenging to diagnose PC due to lack of specific clinical features and biochemical markers. Pathological diagnosis can be troublesome as well, causing a delay in the ideal surgical treatment. Clinical Case: A 39 year old male with history of HTN, recurrent kidney stones, asthma and drug abuse was involuntarily admitted to the hospital by his fiancé after a domestic fight. Initial labs were significant for Calcium 13.2 mg/dl (N 8.8-10.5 mg/dl), Phosphorus 2.8mg/dl (N 2.5-4.5 mg/dl), Magnesium 1.2 mg/dl (N 1.8-2.4 mg/dl), BUN 24 mg/dl (N 6-22mg/dl), Creatinine 2 mg/dl (N 0.8-1.4 mg/dl), CPK 2550 u/l (32-230 u/l). Due to the physical assault, CT Brain and cervical spine were obtained which showed multiple calcified discs and ligaments along with hyperdense vertebral bodies and salt and pepper appearance of the cranial bones. A 2.7 x 2.3 x 4.5 cm mass adjacent to the posterior aspect of the left thyroid lobe concerning for possible parathyroid adenoma or thyroid neoplasm was also reported. Patient was treated with IV fluids and further investigation revealed iPTH 194 pg/ml (N 15-65 pg/ml), ca 12.7 mg/dl, Vit D(OH)25 - 21 ng/ml. Thyroid US and NM Parathyroid imaging confirmed a large 6 x 2.5 x 2.3 cm left superior parathyroid.The patient underwent parathyroidectomy, intraoperatively PTH dropped from 233 to 64 pg/ml. Kidney function and calcium normalized after the surgery. The patient was screened for MEN due to hyperparathyroidism and resistant hypertension. Gastrin, calcitonin, catecholamines were all within the normal range. During the surgery, a very large gland was noted without any local invasion. Gross pathologic examination of the specimen showed a markedly enlarged, fragmented and hemorrhagic parathyroid (12.6 gm). Histologically, tumor demonstrated uniform oxyphil cells with focal cellular atypia and low mitotic rate, divided by thick fibrous bands. No definitive vascular invasion was seen, however, peripheral nerve entrapment was noted. Fragmentation of the specimen with limited representation of the tumor stroma interface precluded accurate evaluation of capsular invasion and made this a difficult case to diagnose. The specimen was sent to Johns Hopkins for further evaluation. An immunostain for parafibromin demonstrated abnormal loss of nuclear expression, a finding that is 95% specific for parathyroid carcinoma. Based on the combination of these atypical features, the loss of parafibromin staining, entrapment of peripheral nerve, and the markedly enlarged parathyroid, the lesion were best regarded as a low-grade parathyroid carcinoma. Conclusion: PC is often a difficult pre-operative diagnosis and the patients are subjected to recurrent surgeries. Our patient underwent left thyroid lobectomy after the pathological confirmation of PC.