The pituitary tumor occurs due to uncontrolled growth and division of the cells of the pituitary gland, resulting in abnormal tissue growth in the pituitary gland. As the pituitary gland secretes several hormones, most patients with pituitary tumors have excessive levels of specific hormones, resulting in various symptoms. There are several types of pituitary tumors. Early diagnosis and optimal treatment improve overall outcomes.
What is a Pituitary Adenoma?
A pituitary adenoma is a benign (non-cancerous) tissue growth in the pituitary gland. Unlike cancerous or malignant growths, pituitary adenoma does not have the potential to spread to other organs. Most of the pituitary adenomas are located in the front part (anterior segment) of the pituitary gland. Although pituitary adenoma may occur at any age, people in their 30s and 40s are at increased risk of developing pituitary adenoma. The symptoms of pituitary adenoma may be either due to pressure exerted by the tumor on the surrounding structures or the secretion of hormones from the adenoma (functioning adenoma).
What is a Pituitary Tumor?
Cells have prespecified multiplication, growth, and death rates based on the information stored in the genes. However, at times, the cells may undergo uncontrolled division due to altered genetic information, resulting in an accumulation of tissues, which is later referred to as a tumor. Most pituitary tumors are non-cancerous (pituitary adenomas). Pituitary gland cancers (pituitary carcinomas), on the other hand, are rare.
Diagnosing pituitary carcinoma is challenging, as the cells of pituitary carcinoma look similar to pituitary adenoma under the microscope. The only way to determine the presence of pituitary carcinoma is when it spreads to other body parts distant from the pituitary gland. Most often, the pituitary carcinoma spreads to the spinal cord, brain, and meninges. Rarely does the tumor spread to the liver, lungs, or heart.
How Common is a Pituitary Tumor?
Pituitary tumors are relatively common. Fortunately, most are benign (adenomas), and very few are cancerous (carcinomas). It has been reported that approximately 10% of autopsies have incidental pituitary tumors. In addition, there is an increase in incidentally found pituitary lesions and clinically meaningful pituitary adenomas due to increased MRI availability. The epidemiological studies suggest the incidence of pituitary adenoma is between 3.9 and 7.4 cases per 100,000 per year, and the prevalence is between 76 and 116 cases per 100,000 population. Most new cases diagnosed with pituitary adenomas include non-secreting pituitary adenomas and prolactinomas. There is clinical heterogeneity with pituitary adenomas. Most of the clinically meaningful pituitary adenomas occur in females.
What are the Most Common Types of Pituitary Tumors?
Some of the most common types of pituitary tumors are:
Functional Pituitary Tumor
A functioning pituitary tumor is one of the types of pituitary tumors that produce excessive hormones. Functioning pituitary tumors are further subdivided into various types based on the secretion of specific hormones:
Nonfunctional Pituitary Tumor
Non-functional pituitary tumors do not result in excessive hormonal secretion and, thus, do not alter serum hormone levels. The symptoms of non-functional pituitary tumors depend on the tumor size and the extent of invasion into the surrounding tissues. In some patients with non-functional pituitary tumors, the patients may have hormonal deficiencies due to pituitary dysfunction.
Macroadenoma Pituitary Tumor
Tumors of a size less than 1 cm are pituitary microadenomas.
Microadenoma Pituitary Tumor
Tumors that are 1 cm or greater in size are classified as macroadenomas. Adenomas greater than 4 cm in size are called giant adenomas.
Are Pituitary Tumors Staged?
Unlike other cancer types, there are no pituitary tumor stages. Treatment is based on the individual characteristics of the tumor. The tumors are classified based on the findings of the oncologists. The classification is based on the size, hormonal secretions, and their effect on the surrounding tissues. The following are some of the different characteristics of a pituitary tumor:
Functioning and Non-Functioning: Functional pituitary tumors secrete excessive hormones, while non-functional tumors do not actively produce hormones. The symptoms presented by functioning tumors are due to excessive hormone levels. The oncologists also determine the types of hormones secreted by the tumor. The symptoms of non-functioning tumors are due to the compression of the surrounding structures.
Invasiveness: Oncologists also obtain information regarding the extent of the spread of the tumor to nearby tissues. MRI can provide this information.
Is a Pituitary Adenoma a Brain Tumor?
This is controversial, as some scientists call pituitary adenoma a brain tumor, while others do not consider it a brain tumor. The scientists who are against calling it a brain tumor suggest that the pituitary gland is not a part of the brain and is rather located below the brain and above the nasal passage. Frontiers in Endocrinology, in an article published in 2021, called pituitary tumors the second most common primary brain tumor in humans.
Conclusion
Uncontrolled growth of cells in the pituitary gland results in pituitary tumors. Fortunately, most of these tumors are benign. The tumors may either secrete excessive hormones and/or compress the surrounding structures. Staging of the pituitary tumors is not done like in other cancers.
