Diagnosing Parathyroid Cancer

Parathyroid cancer is not easy to diagnose. It is often difficult to distinguish between a benign parathyroid tumor and parathyroid cancer. Therefore, a variety of tests may be used to establish a diagnosis.
Neck palpation

This simple test, which involves your doctor feeling the area around the front of your neck near the thyroid gland, may reveal a cancerous parathyroid tumor. More than 30 percent of parathyroid cancers present with a palpable neck mass.
Blood tests

Parathyroid hormone level
Extremely high levels of parathyroid hormone (PTH) may indicate parathyroid cancer yet benign parathyroid adenomas also cause elevated parathyroid hormone levels. Generally, the levels seen in parathyroid cancer are significantly higher.

Serum calcium level
Increased PTH production from either a benign parathyroid adenoma or a malignant parathyroid carcinoma, results in hypercalcemia, producing substantially elevated serum calcium levels. Patients with serum calcium levels exceeding 14 mg/dL, particularly those with a palpable neck mass, may be more likely to have parathyroid cancer.

Alkaline phosphatase level
In many cancers, increased alkaline phosphatase levels serve as a tumor marker indicating bone metastases. In parathyroid cancer, the mobilization of calcium from the bones to the blood also causes alkaline phosphatase levels to increase. These levels are generally elevated significantly beyond the normal range in parathyroid cancer patients

Renal function tests
Certain indicators of renal function such as levels of blood urea nitrogen and creatinine, are more likely to be abnormal in parathyroid cancer.

Sestamibi Scan
In this test, your doctor injects a solution of the radioactive isotope Technetium-99m-sestamibi (sestamibi is the name of the molecule to which the technetium is attached) intravenously. The technetium emits low-energy gamma rays, which can be counted and turned into an image by a “gamma camera” in a process known as scintigraphy.

The premise of the test is that the radiolabeled sestamibi is absorbed by hyperfunctioning (overactive) parathyroid glands, but not in normal parathyroid glands. Therefore, the malfunctioning gland (whether it is a benign adenoma or a malignant carcinoma) can be precisely identified.

To further characterize your parathyroid tumor, your doctor may suggest an ultrasound. This simple, quick and painless test passes a wand, called a transducer, which emits sound waves, over the neck area to produce an image. Based on this image, your doctor can determine the size, shape and exact location of the parathyroid tumor.

CT, MRI and PET scans
Computed tomography (CT) and magnetic resonance imaging (MRI) scans are sometimes used to stage parathyroid cancer. Staging means gauging the extent of spread of the cancer. They are also used to check for recurrence of the cancer in the neck and if it has spread to other parts of the body. However, CT or MRI scans are rarely used for a definitive initial diagnosis. Posititron emission tomography (PET) scans use a modified sugar compound called fluorodeoxyglucose (FDG). The scan picks up areas of cells that preferentially absorb the FDG. PET scans are also useful to assess spread throughout the neck and in order to monitor for possible recurrence.

Venous sampling
If imaging tests do not show which parathyroid gland is overactive, blood samples may be taken from veins near each parathyroid gland to find which one is making too much PTH.

Unlike in thyroid cancer, biopsy in parathyroid cancer is typically not recommended. If your doctor suspects parathyroid cancer and intends on doing a biopsy to confirm it, you may wish to seek a second opinion. This is because in doing a parathyroid biopsy, there is a significant risk that the capsule of the parathyroid may rupture, causing microscopic tumor cells to seed, or spread – a disastrous consequence.