Diagnosis and Treatment of Parathyroid Cancer
Parathyroid cancer is extremely rare.
Almost all parathyroid problems are caused by one or more of the parathyroid glands producing too much parathyroid hormone (PTH). This is called hyperparathyroidism, and it causes a number of medical problems such as osteoporosis, mental disorders, ulcers, pancreatitis, kidney stones, and other symptoms. However, the overgrowth of parathyroid tissues responsible for this overproduction of PTH is not malignant, and therefore, these overgrowths are usually referred to as parathyroid adenomas (benign parathyroid hormone secreting tumors).
Parathyroid disease is caused by a single bad parathyroid gland more than 90% of the time. Since there are 4 parathyroid glands, removing one bad gland becomes the simple way to cure the problem.
Parathyroid glands are no different than every other tissue in the human body—they can develop cancer in them. Parathyroid cancer, however, is extremely rare, with only a few dozen cases seen every year in the US. Parathyroid cancer is so rare that most doctors have never seen it.
Very rarely, a parathyroid gland will become cancerous (the overgrowth is composed of malignant cells). Since parathyroid cells make parathyroid hormone (PTH) as their only purpose in life, those that are cancerous (growing out of control) will make PTH "out of control" as well.
In fact, that is a big tip-off that a patient with hyperparathyroidism might have parathyroid cancer since these malignant tumors will produce "massive" amounts of parathyroid hormone instead of "large" amounts like are seen with benign parathyroid tumors (adenomas or hyperplasia). All patients with hyperparathyroidism have elevated parathyroid horomone in their blood, those with benign disease tend to have levels in the "hundreds" where as those with parathyroid cancer tend to have values in the "thousands."
Facts about Parathyroid Cancer
- Parathyroid cancer is very rare: about one case in every 1,000 patients with parathyroid disease, or possibly even rarer.
- Parathyroid cancer is often mild and not very aggressive.
- Parathyroid cancer is often hard for the pathologist to diagnose under the microscope. Thus the diagnosis often depends on the clinical picture (very high parathyroid hormone levels, and very high serum calcium levels).
- Parathyroid cancer is almost always associated with extremely high parathyroid hormone (PTH) levels (typically in the thousands).
- If your parathyroid hormone level is not in the thousands, and your calcium in not consistently over 14, you do not have parathyroid cancer (a generalization, but a good one).
- Most people with calcium levels above 14 still do not have parathyroid cancer.
- Parathyroid cancer is usually associated with extremely high blood calcium levels (over 14 or 15). The "massive" amounts of parathyroid hormone mobilizes huge amounts of calcium from the bones, releasing this calcium into the blood stream.
- Parathyroid cancer is occasionally associated with a genetic defect, therefore, parathyroid cancer can run in families.
- Like most cancers, the chance of cure from parathyroid cancer is highest if it's found and treated early.
- The prognosis of parathyroid cancer depends on whether the cancer is contained within the parathyroid gland or has spread (metastasized) to other areas (lymph nodes, lung tissue, etc.).
- Parathyroid tumors can reappear as much as 30 years later, so patients with this disease must be examined at least yearly for many years.
Since parathyroid cancers typically make huge amounts of parathyroid hormone (PTH), the effectiveness of the original operation to remove all the cancer can be examined by measuring serum parathyroid hormone levels post-operatively (Note: these very high levels often will take several months to come down to normal after a successful operation).
- The amount of parathyroid hormone in the blood should be tested regularly for years to determine if the parathyroid cancer is recurring (coming back). (This is not true for ordinary hyperparathyroidism patients who developed their disease because of an overgrowth of benign parathyroid tissues—adenomas and hyperplasia).
- Serum calcium levels should also be checked at regular intervals for years post-operatively since they will rise in response to rising parathyroid hormone levels should the cancer return.
- Radioguided parathyroid surgery works extremely well. Radioguided techniques should be used for patients with parathyroid cancer—to help the surgeon know if there are any lymph nodes in the neck that have metastatic parathyroid cancer, and to let the surgeon know when all of the parathyroid tumor has been removed from in and around the thyroid gland.
Parathyroid Cancer Treatment Overview
There are treatments for all patients with parathyroid cancer. Two kinds of treatment are used: surgery (surgical removal of the parathyroid cancer and any nearby tissues which are affected), and radiation therapy(using high-dose x-rays to kill cancer cells). Chemotherapy (using drugs to kill cancer cells) is being studied in a few clinical trials, but there have been no good chemotherapy drugs identified as effective up to this point.
Surgery is the most common and by far the best treatment for parathyroid cancer. Treatment for parathyroid cancer depends on the size of the tumor, its location, and whether or not it has spread to other tissues. The parathyroid gland and the half of the thyroid on the same side as the cancer (thyroid lobectomy) is typically removed.
This is what is shown in this picture* (slightly enlarged). This cancer was almost completely inside the thyroid gland so the thyroid was split in half to expose the parathyroid tumor inside. The cancer is the large round mass in the central and lower portions of the thyroid.
Lymph nodes, if they can be found, are sampled on that side of the neck. The presence of enlarged lymph nodes necessitates a lymph node dissection (removal of all the lymph nodes in that area of the neck). Radiation therapy uses high-energy x-rays to kill cancer cells and shrink tumors, but this is almost never the preferred way in which to treat this cancer initially.
If the tumor reappears after some time, or if it has grown into other structures at the time of the initial operation, then radiation therapy may be an appropriate additional therapy.
*Photo courtesy of James Norman, MD.
Parathyroid hormone is measured annually for many years to check for recurrence. Parathyroid experts note that the malignant, over-active parathyroid cells produce parathyroid hormone. Thus, once it is out, a simple check of the patient's blood will tell if too much parathyroid hormone being produced.
The MIRP procedure (Minimally Invasive Radioguided Parathyroidectomy) works extremely well for parathyroid cancer. Minimally invasive radioguided surgery has been a huge development in the treatment of all forms of parathyroid disease. The concept is to make the hyper-active parathyroid cells radioactive with a mild radioactive substance that is absorbed by the overactive cells.
The surgeon operates using a very small (pencil size) radiation detector and thus can tell where all of the overactive parathyroid cells are located in the body. This works extremely well for all patients with parathyroid disease, including those with parathyroid cancer. We have two articles on the MIRP procedure: Minimal Parathyroid Surgery and The MIRP Operation.
Radioguided parathyroid surgery (MIRP) can be a very useful technique for re-operations. If measuring the parathyroid hormone postoperatively (a few months, or many years later) shows that the parathyroid tumor has recurred (come back in the neck, or metastasized to another part of the body), then a sestamibi scan will typically show where the tumor is located, and a radioguided parathyroid operation can be performed. Once again, the radioactive tumor cells can be found with the probe, and the surgeon (trained in radioguided surgery) can find and remove them. This technique is much more accurate, and it is typically a much less invasive way to treat parathyroid cancer.