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Cancer and Pituitary Tumors

Last Updated: January 7, 2023

Are Pituitary Tumors Benign or Malignant?

"Is my brain tumor cancerous?" is often the first question that comes to mind when diagnosed with any brain tumor type, including a pituitary tumor. Overall, cancerous (malignant) brain tumors usually cause more severe symptoms and often prove more difficult to treat than non-cancerous (benign) ones.  

Almost all pituitary tumors are benign, non-cancerous, and will not significantly affect the lifespan of the patient.

Here is a comprehensive overview of whether pituitary tumors are benign or malignant, and the implications of either diagnosis. This guide also includes insights into diagnosis and treatment options. 

A Brief Overview of Pituitary Tumors

A pituitary tumor is an abnormal growth that develops in the pituitary gland. The pituitary is an important gland that regulates the production of most of the body's hormones – it is commonly referred to as "the master gland." 

Pituitary tumors that produce hormones are called functioning adenomas, while those that do not are called non-functioning adenomas. All functioning adenomas cause various hormone-related symptoms, but only some non-functioning adenomas cause size-related symptoms. 

Size-Related Symptoms of Non-Functioning Pituitary Adenomas

Symptomatic non-functioning adenomas cause symptoms when they press against the pituitary tumor and other critical structures nearby. These are usually large pituitary tumors measuring more than 10 mm and are referred to as macroadenomas. The main symptoms related to a pituitary tumor's size are headaches and vision loss, which can gradually worsen as the tumor grows. 

Hormone-Related Symptoms of Functioning Pituitary Adenomas

Hormones regulate many bodily functions and processes, and hormonal imbalance can cause negative health symptoms. Some of the most common hormone-related symptoms of functioning adenomas include: 

  • Nausea or vomiting
  • Fatigue
  • Depression 
  • Growth problems 
  • Sexual dysfunction 
  • Infertility
  • Unexplained weight gain or loss
  • Disrupted menstruation and early menopause
  • Muscle weakness
  • Easy bruising
  • Impaired sense of smell

Pituitary tumors are relatively common, making up about 17% of all primary brain tumors – the United States reports about 10,000 cases annually. They usually develop in middle-aged individuals in their 30s and 40s, but they can also develop in children or older adults. Fortunately, most pituitary tumors are non-fatal and treatable. Interestingly, many people live their entire lives with pituitary tumors that do not cause symptoms, and the tumor can go undiagnosed. 

Are Pituitary Tumors Cancerous?

Pituitary tumors are categorized into two types based on whether they are cancerous: 

  • Pituitary Adenomas (non-cancerous)
  • Pituitary Carcinomas (cancerous)

Fortunately, most pituitary tumors are not cancerous – pituitary carcinomas are very rare. Because they occur so rarely, research on the frequency and prevalence of cancerous pituitary tumors is inconclusive. Some estimate that pituitary carcinomas account for 0.1% of all pituitary tumors.

Why Does It Matter Whether a Pituitary Tumor Is Cancerous?

Whether a pituitary tumor is cancerous can have many implications on your overall health. It can also affect the tumor's treatment options and your overall quality of life and survival rate

Cancerous pituitary tumors cause similar symptoms to non-cancerous ones. However, the most notable implication of a cancerous pituitary tumor is the possibility of the cancerous cells spreading to surrounding tissues and organs. Pituitary carcinomas usually spread to the following organs: 

  • Skull 
  • Brain 
  • Spinal cord 
  • Meninges (the tissue covering the brain and spinal cord) 

The spread of pituitary carcinoma to these vital organs and tissues can compound and worsen your health problems. Ordinarily, most pituitary tumors have slow growth rates – some never grow big enough to pose a medical problem throughout an entire lifespan. In contrast, most cancerous pituitary tumors grow faster, limiting the time available for treatment and your potential survival rate. 

How Can You Tell If a Pituitary Tumor Is Benign or Malignant?

Cancerous pituitary tumors closely resemble non-cancerous ones, making them difficult to differentiate. Unfortunately, diagnostic solutions for cancerous pituitary tumors are not always conclusive or reliable. 

Currently, the way to diagnose a cancerous pituitary tumor is to monitor its growth rate and check for spread to sites elsewhere in the body. In very rare cases, some non-cancerous pituitary tumors can become cancerous over time. Thus, a diagnosis of pituitary tumor often requires regular monitoring to promptly conduct additional tests and administer treatment if malignancy is suspected.

Diagnosing Cancerous & Non-Cancerous Pituitary Tumors

Cancerous pituitary tumors are difficult to detect, and both types are diagnosed the same way. Besides a thorough medical history and physical exam, diagnosing pituitary tumors involves the following tests: 

  • Blood and urine tests to measure the body's hormone levels (for functioning adenomas)
  • MRI tests and CT scans to visualize the brain and pituitary gland

Rarely, a biopsy to test for the presence of cancerous cells may be performed. However, this is a surgical procedure that rarely risks injuring the pituitary gland and surrounding structures. If surgery is not already part of the treatment plan, biopsies are often not performed because blood and imaging tests usually suffice for making the diagnosis.

Treating Cancerous & Non-Cancerous Pituitary Tumors

Fortunately, most pituitary tumors are treatable. However, cancerous pituitary tumors are more complicated to treat because of their accelerated growth and tendency to recur and spread to other locations in the body. Treatment for a pituitary tumor depends on the specific type of tumor and includes the following options.

Surgery 

Surgery is an effective treatment for cancerous and non-cancerous pituitary tumors. The transsphenoidal surgical technique is often the preferred approach. This involves accessing the tumor through the nose using long instruments and small cameras to visualize and remove the tumor. For larger or more complicated pituitary tumors, a more invasive transcranial surgical technique may be used where the surgeon accesses the pituitary gland by creating an opening on the front of the skull (craniotomy).

Radiation Therapy 

Radiation therapy uses high-energy x-rays to destroy abnormal pituitary tumor cells. Radiation therapy may be offered after surgery to inhibit growth of any remaining abnormal cells. It can also be rarely recommended instead of surgery and medication therapy if the latter options are not applicable. 

Medication Therapy 

Medication therapy is usually the first course of treatment for pituitary tumors that secrete the hormone prolactin (prolactinoma). Medications such as cabergoline or bromocriptine are often effective at shrinking the prolactinoma, and no surgery is usually necessary. If medications are ineffective or cannot be tolerated, other treatment options such as surgery or radiation therapy may be pursued.

Key Takeaways

Cancerous pituitary adenomas are exceedingly rare and are usually diagnosed by monitoring their rate of growth and spread to other organs. Fortunately, most pituitary tumors are non-cancerous and treatable. Surgery, radiation therapy, and medications are effective treatment options.

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