Unusual Presentation of Parathyroid Carcinoma: A Case Report

Presentation Number: LB MON 48
Date of Presentation: April 3rd, 2017

Marcella Menezes Andrade, Barbara C Silva*, Ana Paula C Rocha, Fabiano F M Prado, André Luis R Muniz and Thiago Bechara Noviello
Santa Casa de Belo Horizonte

Abstract

Background: Parathyroid carcinoma is a rare disease, accounting for less than 1% of the cases of primary hyperparathyroidism (PHPT). Distant metastases occur late, most frequently to the lungs and liver. We report a rare case of a parathyroid carcinoma presented as a small parathyroid lesion, not identified in the imaging studies, with distant metastasis to the costal arch.

Clinical case: A 49-year-old woman was referred to a tertiary hospital due to myalgia, weight loss and fatigue, leading her to be bedridden. Laboratory tests revealed markedly elevated calcium (17.7mg/dL, n8.8-10.6mg/dL) and PTH (1754pg/mL, n<68pg/mL), low GFR (23 mL/min, n>60mL/min), hypercalciuria (468mg/24h, n<250mg/24h), low 25-OH-vitamin D (13.7ng/mL, n>20ng/mL), and a normal phosphate concentration. Both neck ultrasound and 99mTc-MDP scintigraphy were negative for parathyroid lesions. Abdominal ultrasound revealed nephrolitiasis. Based on the diagnosis of PHPT, the patient underwent bilateral neck exploration, which did not identify an enlarged parathyroid gland. Total parathyroidectomy was performed, with autotransplantation of parathyroid tissue into the forearm. Pathology of 1 of the 4 glands removed revealed a 2cm, encapsulated lesion, without local extension but with vascular invasion. Histological features could not distinguish between a benign parathyroid adenoma from parathyroid carcinoma. The remained parathyroid glands were described as normal. Following the surgery, further evaluation showed persistent PHPT (serum calcium 11.7mg/dL and PTH 1587pg/mL). A 99mTc-MDP whole-body scan was negative for parathyroid implants, but a CT scan of the chest revealed a 3.5cm, solid, heterogeneous, calcified nodule in the third left costal arch. A CT-guided core-needle biopsy (CNB) of the nodule was performed and, although no malignancy was found in the pathology, the PTH concentration in the CNB wash was 15000pg/mL. The third left costal arch was then removed, and the pathology revealed a “metastatic adenocarcinoma”. Two days following the surgery the patient had her symptoms improved and the PTH serum level decreased to 237pg/mL. Hypocalcemia (7.8mg/dL) was noted 6 days after the operation, and the patient was discharged on calcium supplements and calcitriol, with a PTH of 313 pg/mL, normal calcium and phosphate serum levels, and progressive improvement of her renal function.

Conclusion: This is the first report to describe a metastatic parathyroid carcinoma at the costal arch, diagnosed through the measurement of PTH in the CNB wash. Of note, both the primary parathyroid tumor and the bone implant were not seen on the 99mTc-MDP scan, and the distant metastasis occurred without prior local dissemination of the tumor. The prognosis of parathyroid carcinoma is quite variable, but the identification and resection of the primary tumor and metastatic lesions are essential to improve patients’ survival.

 

Nothing to Disclose: MMA, BCS, APCR, FFMP, ALRM, TBN