A pituitary microadenoma is a benign tumor of the pituitary gland with a diameter less than 10 mm (those with a diameter greater than 10 mm are called macroadenomas).
How common are pituitary microadenomas?
Microadenomas can occur in either sex. As many as 10 percent of the population may have a microadenoma, but most do not cause symptoms. Prolactinomas, a subset of microadenomas, are diagnosed more frequently in women, possibly because of the more striking presenting features such as amenorrhea, galactorrhea, or both.
In men, the diagnosis of inactive adenomas is often delayed until they have become macroadenomas and cause symptoms by compressing nearby structures. Microadenomas can occur at any age, but prevalence appears to increase with age.
How are pituitary microadenomas diagnosed?
Your doctor may suspect you have a microadenoma if you have the symptoms listed above. Possible tests to confirm this diagnosis include the following:
- Blood tests
- Urine tests
- Visual field tests
- Computed tomography (CT)
- Magnetic resonance imaging (MRI)
- Inferior petrosal sinus sampling (IPSS)
Pituitary microadenomas can cause Cushing’s disease, acromegaly, hyperthyroidism, and rarely, symptoms related to decreased secretion from the pituitary gland.
Symptoms of a pituitary microadenoma may include the following:
- Vision problems
- Menstrual or breast changes
- Unexplained hair growth or loss
For prolactin-secreting microadenomas, surgical removal is followed by recurrence in about 30 percent of patients. Therefore, medical therapy that blocks the hormonal effects of the tumor and prevents or shrinks its growth is preferred.
Surgery is the best form of treatment and the only way to achieve a cure. Your surgeon will gain access to your pituitary gland using the transsphenoidal approach—so named because the route your surgeon takes crosses, or transects, your sphenoid bone. This bone is located behind your nose mostly within your skull.
Using precise surgical instruments, your surgeon will make an incision through your nasal cavity to create an opening in your sphenoid bone. Once your surgeon gains access to your sphenoid sinus (the air-filled area behind the sphenoid bone), further incisions will be made until a hole is created in the sella turcica—the bone that cradles and protects your pituitary gland.
After your tumor appears in the operative field, removal of the tumor can proceed. Your surgeon will use high magnification to readily distinguish normal pituitary tissue from the microadenoma.
Once the tumor has been removed, your surgeon will clean the tumor cavity and seal it.
At Barrow Neurological Institute at Dignity Health St. Joseph’s Hospital and Medical Center, our surgeons specialize in two types of surgery for pituitary microadenomas:
- Microsurgery uses a powerful operating microscope to help your surgeon distinguish between tiny structures in and around your pituitary gland
- Endoscopic surgery uses small tubes and a tiny camera to help your surgeon remove your tumor in small pieces
Both surgeries aim to minimize trauma to the tissue surrounding your pituitary gland while facilitating a speedy recovery with as little pain or discomfort as is possible. Each technique has its own inherent advantages and disadvantages, and your surgeons will work with you to help determine which is the best fit for you.
Most patients are able to return home the day after their surgery for removing a pituitary microadenoma, and nasal packing is seldom required.
Gamma Knife radiosurgery is a highly advanced form of radiotherapy that is used to achieve similar results to the traditional surgical techniques described above. However, with Gamma Knife it can take several years for elevated hormone levels to return to normal, rather than days or weeks as with traditional surgery.
The ‘knife’ in this surgery is actually made up of many small beams of radiation focused on a single point. Each individual beam is too weak to damage healthy tissue, but at the point where the beams converge they deliver a dose of radiation that is lethal to the tumor.
Gamma Knife is an outpatient procedure, does not involve any incisions, and requires only brief sedation under general anesthetic.
- Date of last review: September 18, 2017
- Author: Andrew S. Little, MD