The pituitary gland lies at the base of the brain and contains a number of specialized cells. The gland functions to secrete a number of hormones, which then travel throughout the body in the bloodstream to trigger biological responses in tissues. A pituitary germinoma is a benign or malignant tumor containing cells that resemble germ cells---immature stem cells. These tumors are typically aggressive and invasive, and possess a number of characteristics that prove important in patient prognosis and tumor treatment.
Inflammatory Responses in the Brain
One characteristic of pituitary germinomas is their ability to generate an inflammatory response within the brain. Brain tumor growth can increase the level of inflammation in the brain, since tumors may obstruct the natural flow of cerebrospinal fluid and cause a fluid buildup that irritates brain tissue. A study published in "Pituitary" in 2009 reports that the growth of a pituitary germinoma can lead to symptoms resembling those of autoimmune diseases. The pituitary germinoma can recruit lymphocytes, a type of white blood cell, to the site of tumor growth. These lymphocytes and the surrounding cells secrete inflammatory factors, leading to sustained inflammation in the brain, which in turn recruits more lymphocytes. This sustained inflammation can lead to swelling of the brain and potentiate the symptoms of the pituitary tumor.
Sensitivity to Radiation
Cells within a pituitary germinoma resemble stem cells, a type of cell that continually proliferates within the body under normal conditions. The cells within the germinoma also proliferate very rapidly to give rise to new tumor cells, and this rapid proliferation makes pituitary germinoma cells sensitive to radiation. During radiotherapy, exposure to radiation damages cellular DNA, and particularly affects rapidly proliferating cells. A study published in the Journal of Chinese Clinical Medicine in 2007 indicates that radiation treatment is very successful in treating germinomas, leading to a recovery rate of 95 percent of 57 patients. This characteristic of germinomas is useful for doctors treating adults with tumor. The study warns, however, that treating children under the age of 15 with radiation can cause brain damage, and they may require alternate therapies to avoid the long-term side effects of this treatment.
CEA Secretion
Some pituitary germinoma cells secrete CEA, or carcinoembryonic antigen. This protein, normally found on the surface of nonspecialized stem cells, can also become expressed on cancer cells that resemble stem cells, such as those in germinomas. The rapid proliferation and abnormal behavior of the tumor cells causes CEA to leak into the fluid around the tumor, and the presence of a germinoma may be accompanied by an increase in CEA within the cerebrospinal fluid, reports the UCLA Health System. As a result, doctors can exploit this characteristic of pituitary germinomas and test CEA levels in the cerebrospinal fluid to help diagnose the tumor before resorting to more invasive or painful diagnostic procedures.
