Endocrine Abstracts

Introduction: Parathyroid cancer is a rare endocrine malignancy and constitutes 0.005% of all cancers. It can recur in 50% of cases. The first recurrence commonly occurs within 3 years of the original diagnosis. Hypercalcaemia is the main cause of morbidity and mortality. We present a case of a 62-year-old male patient who had an atypical lung nodule recurrence with normal calcium and PTH levels, six years following resection of a functioning parathyroid cancer.

Case Report: A 62-year-old male patient was referred to endocrinology due to hypercalcaemia post resection of adenocarcinoma of the rectum. Post-bowel surgery, his serum calcium levels ranged from 3.07 to 3.71 mmol/litre (2.10-2.60), serum PTH 16.1 pmol/litre (1.2-6.9), and vitamin D3 43.6 nmol/litre (>50). A parathyroid sestamibi scan revealed right superior parathyroid adenoma and an intrathyroidal mass suspicious of parathyroid tissue. He underwent a right hemi-thyroidectomy and bilateral superior parathyroidectomy. Histology confirmed a parathyroid carcinoma in the intrathyroidal tissue with normal superior parathyroid glands. He was monitored annually by endocrinologists and surgeons. This was done by checking his serum calcium, PTH, and ultrasound neck which all remained normal. Six years following the parathyroid surgery, he was found to have an enlarging lung nodule on surveillance imaging for his rectal cancer. A CT-guided lung biopsy confirmed a parathyroid cancer metastasis. A PET CT scan and ultrasound of the neck did not reveal any evidence of local recurrence. The lung nodule was resected which confirmed a parathyroid cancer metastasis.

Discussion/Conclusions: Long-term survival is possible with recurrence of parathyroid cancer and routine surveillance can identify early recurrence. However, there is no clear consensus guidance on the follow-up of patients with parathyroid cancer. The existing guidelines recommend regular surveillance of functioning parathyroid cancer by performing serum calcium, PTH, and ultrasound neck. Our case is atypical in that the patient did not have hypercalcaemia at the time of recurrence despite the originally resected functional parathyroid cancer. If surveillance imaging for rectal cancer had not been done, the lung nodule may not have been picked up in a timely manner. This case highlights the need for lifelong follow-up for parathyroid cancer patients. Current guidelines should be reviewed to include whole-body imaging modalities to pick up early distant recurrence. Our case also highlights that recurrence of functional parathyroid cancer might not present with hypercalcaemia.