Parathyroid carcinoma (PC) is an uncommon endocrine malignancy of the parathyroid glands. It represents only about 1% of all parathyroid tumors and its co-occurence with papillary thyroid carcinoma (PTC) is rare.

This is a case of 47-year-old woman presenting with elevated serum calcium levels, nephrocalcinosis and renal failure. Neck ultrasonography showed a parathyroid adenoma with thyroid nodules on both thyroid lobes. Parathyroid scintigraphy using 99m Tc-Sestamibi showed focal uptake and retention in the mid-lateral left lobe suggestive of parathyroid adenoma or hyperplasia. Patient was eventually subjected to parathyroidectomy and total thyroidectomy. Intraoperative PTH monitoring showed 93% decrease from 5470 pg/mL to 356.1 pg/mL within 10 minutes from gland excision which confirms successful removal of the culprit parathyroid gland. Histopathology confirmed the presence of both parathyroid carcinoma and papillary thyroid carcinoma on the right thyroid nodule.

Postoperatively, patient had severe hypocalcemia at 36 hours postsurgery, iCa 0.7 mmol/L, causing generalized paresthesia, facial twitching and carpopedal spasm. Supplemental intravenous and oral calcium were given until patient had stable serum calcium levels. stable. Hemodialysis was likewise continued after hospital discharge. On follow up, the patient was readmitted due to severe hypocalcemia. Radioactive iodine (RAI) 131 treatment for PTC was also offered however patient did not consent.

PC is a rare cause of primary hyperparathyroidism presenting with severe hypercalcemia compared to a parathyroid adenoma. It may present with bone and renal complications such as fragility fractures and nephrolithiasis. The co-occurence of parathyroid carcinoma and papillary thyroid carcinoma is not common. Aside from hypercalcemia, most presents with fatigue, weakness, decreased appetite and digestive symptoms, and also psychiatric manifestations such as depression. Literatures have reported at least 15 cases of PC with Papillary Thyroid Carcinoma. Majority of the documented cases were female with ages ranging from 21-79 years. Of the associated thyroid carcinomas, Hurthle cell variant was associated with poorer prognosis and higher rates of recurrence in local lymph nodes. In our case, histopathology report revealed PC and PTCA with oncocytic features which on literatures may be more aggressive than the classical variants. Literatures suggests that RAI may improve overall survival in patients with differentiated oncocytic follicular cell thyroid carcinomas. However, we recognize the challenge of administration of RAI in patients on hemodialysis as it requires multidisciplinary coordination due to the differences in renal clearance of I-131 and its dose, exposure to staff and the contamination of the dialysis machine.