Types of Pituitary Tumors
The main types of pituitary tumors are adenomas (non-cancerous) and carcinomas (cancerous). Other types of pituitary tumors include microadenomas and macroadenomas. Pituitary tumors are categorized even further based on whether or not they produce hormones and what kinds of hormones are produced. Examples of these forms of pituitary tumors include prolactin-producing tumors (prolactinomas), ACTH-producing tumors, and nonfunctioning pituitary adenomas.
There are several types of pituitary tumors. A pituitary tumor is first grouped based on whether it is cancerous or not. Most pituitary tumors are not cancerous. These pituitary tumors are called adenomas. A pituitary adenoma is classified based on its size:
- Microadenomas are smaller than 10 millimeters.
- Macroadenomas are 10 millimeters or larger.
Most pituitary adenomas are microadenomas.
Pituitary tumors that are cancerous are called carcinomas. These are pituitary tumors that can spread far from the pituitary gland into the central nervous system (brain and spinal cord) or outside of the central nervous system. Similar to the adenomas, carcinomas can make pituitary hormones, most commonly ACTH (adrenocorticotropin) and prolactin.
Pituitary adenomas are also classified based on whether they produce hormones or not. Pituitary tumors that make one or more of the pituitary hormones are called functioning pituitary tumors, while those that do not make hormones are called nonfunctioning pituitary tumors. Each type of functioning pituitary tumor causes different symptoms, depending on the type of hormone that is being made by the tumor. Examples of functioning pituitary tumors include:
- Prolactin-producing tumors (which make up about 43 percent of all pituitary adenomas)
- ACTH-producing tumors (which account for about 7 percent of all pituitary adenomas)
- Growth hormone-producing tumors (which make up about 17 percent of all pituitary adenomas)
- Thyroid hormone-producing tumors (which account for about 3 percent of all pituitary adenomas).
Nonfunctioning adenomas make up the remaining 30 percent of all pituitary adenomas.