Is a Parathyroid Adenoma Cancerous?
No, a single parathyroid adenoma causing primary hyperparathyroidism is not cancerous—it is a benign tumor. Parathyroid adenomas account for 80-85% of primary hyperparathyroidism cases and are benign neoplasms, not malignancies. 1, 2
Benign Nature of Parathyroid Adenomas
Parathyroid adenomas are benign tumors that cause excessive and abnormally regulated secretion of parathyroid hormone, leading to hypercalcemia and the metabolic disturbances you're observing. 2
Single-gland parathyroid adenomas are the typical presentation in sporadic primary hyperparathyroidism, representing the vast majority of cases in patients without genetic syndromes. 3
After surgical removal of a parathyroid adenoma, serum calcium levels return to normal immediately, confirming the benign but hyperfunctioning nature of these lesions. 1, 4, 2
When to Consider Parathyroid Carcinoma
While parathyroid adenomas are benign, you should be aware of the rare entity of parathyroid carcinoma, which occurs in approximately 15% of patients with CDC73-related (Hyperparathyroid-Jaw Tumor) syndrome. 3
Red Flags for Malignancy:
Loss of nuclear parafibromin staining on immunohistochemistry of any parathyroid neoplasm should prompt consideration of germline CDC73 analysis and raises concern for carcinoma. 3
Clinical features suggesting carcinoma include extremely high PTH levels (often >5-10 times normal), palpable neck mass, vocal cord paralysis, or severe hypercalcemia (>14 mg/dL). 3
Parafibromin immunohistochemistry should be performed on all parathyroid neoplasms in young patients, as it may help distinguish adenomatous from carcinomatous nodules. 3
Genetic Syndromes to Consider
In the context of a young patient or family history, consider:
CDC73-related syndrome can present with parathyroid adenomas as young as age 7 years, with approximately 15% developing parathyroid carcinoma. 3
MEN4 syndrome (CDKN1B variants) typically presents later (youngest reported at age 30) and is associated with parathyroid adenomas, not carcinomas. 3
MEN1 syndrome causes parathyroid adenomas or hyperplasia, not carcinomas. 3
Clinical Management Implications
Surgical excision (parathyroidectomy) is the definitive treatment for symptomatic primary hyperparathyroidism due to parathyroid adenoma, and it is curative for this benign condition. 5
Surgery is indicated even when asymptomatic given the potential negative effects of long-term hypercalcemia on bones, kidneys, and cardiovascular system. 5
Biopsy of suspicious neck lesions is discouraged in patients with suspected parathyroid disease due to risk of seeding and capsular disruption. 3
Common Pitfall
The most important pitfall is assuming all hypercalcemia in cancer patients is due to malignancy-associated hypercalcemia. In fact, patients with known malignancies can have concomitant primary hyperparathyroidism from benign parathyroid adenomas—18 such cases were documented with various cancers (colon, breast, lymphoma, thyroid), and all were cured by parathyroidectomy. 1