Predicting the Presence of Parathyroid Carcinoma

Excerpt

In this issue of Annals of Surgical Oncology, Robert et al.1 report their experience with 9 patients with parathyroid carcinoma and compare the preoperative presentation and histopathologic findings in these 9 patients with those in a larger group of 302 patients who underwent parathyroidectomy for benign disease. Parathyroid carcinoma is a rare disease, with a prevalence of .005% of all cancers.2 There is ample documentation in the literature that patients with parathyroid cancer tend to present, as described here, with higher serum calcium levels (70% have levels >14 mg/dL) and higher parathyroid hormone levels (>5 times normal) and are more likely to have associated metabolic symptoms than corresponding patients with benign hyperparathyroidism. In addition, approximately 40% of patients with parathyroid carcinoma present with a palpable neck mass3,4; this finding is very uncommon in patients with benign hyperparathyroidism. As Robert et al. demonstrate, a definitive preoperative diagnosis of parathyroid carcinoma is impossible to make, because the metabolic manifestations of parathyroid cancer overlap with those of adenomas. A high index of suspicion must be maintained to achieve remarkably good results such as those reported in this series: none of the nine patients with parathyroid carcinoma had a recurrence. These results are favorable compared with those in the literature and highlight the importance of appropriate surgical treatment of patients who present with clinical or operative findings suggestive of parathyroid carcinoma. In addition to the presence of a high serum calcium, a high parathyroid hormone level, marked metabolic symptoms, and a palpable neck mass, palsy of the recurrent laryngeal nerve in a patient with hyperparathyroidism is also suggestive of parathyroid cancer. Preoperative fine-needle aspiration biopsy is contraindicated in patients with suspected parathyroid cancer because of the risk of local dissemination, and intraoperative frozen section evaluation is unreliable. Intraoperative clinical recognition of the presence of parathyroid carcinoma is therefore essential. Parathyroid cancer should be suspected in the presence of a gray, firm, adherent parathyroid gland. Parathyroid cancer frequently recurs in the central neck and typically exhibits a natural history marked by recurrent hypercalcemia. Most patients who have recurrences after initial surgery will ultimately die of cancer-related causes, usually of the metabolic complications of hypercalcemia.5,6 Therefore, performance of the appropriate surgical procedure during the initial operation is critical. En-bloc resection of the tumor and areas of potential invasion is indicated. The integrity of the parathyroid capsule should be maintained during dissection by performance of an en-bloc resection of the ipsilateral central neck contents, including the thyroid lobe and tracheoesophageal soft tissues and lymphatics. Recurrent parathyroid carcinoma can be an indolent disease with morbidity and mortality related to hypercalcemia. Therefore, it is reasonable to consider palliative surgery to control hypercalcemia, even in selected patients with metastatic disease. The role of locoregional radiotherapy in the treatment of patients with parathyroid carcinoma remains controversial. Although adjuvant radiotherapy may improve local control and limit the occurrence of local relapse5,7,8 and can be helpful in control of bony metastases, it is probably less effective when it is used after incomplete local surgery. A comprehensive approach to these patients emphasizes a high index of suspicion in patients with suggestive preoperative signs or symptoms, an appropriately aggressive surgical procedure in at-risk patients, and a flexible approach to patients with recurrent cancer that may include surgery, radiotherapy, and medical treatment for hypercalcemia. …