Senator Kennedy is surrounded by his wife and children in the Massachusetts General Hospital.
The type of tumor found in Ted Kennedy's brain is one of the most lethal and difficult to treat. It's known as malignant glioma.
According to experts in the Bay Area, the aggressive nature of this type of cancer could limit treatment options for Kennedy's doctors.
"It's a very serious situation, when dealing with tumor in the brain, it's always a serious situation," said UCSF neuroncology director Dr. Susan Chang.
Dr. Chang recently conducted a large study on malignant glioma at UCSF. She says the tumors are especially dangerous because they form in the brain tissue itself.
"These tumors do not form in localized region that presses on the brain, they infiltrate, so they interspese themselves within the normal tissue," said Dr. Chang. "There's no clear boundary where the tumor is and where the normal tissue is. Surgery is good at removing areas that are safe to remove, but in the brain every part has a function."
According to Kennedy's doctors, his tumor is located in a section of the brain known as the parietal lobe, which is responsible for muscle coordination, elements of speech and the sense of touch -- among other functions.
Depending on its exact placement, and how aggressively the tumor has spread, surgeons could still decide to remove as much of it as possible, without harming the delicate surrounding tissue.
But doctors at Massachusetts General Hospital have not mentioned surgery as an option, leading many to speculate the tumor is inoperable.
"These tumors in general can be very difficult to treat," said Dr. Chang.
Kennedy's doctors could decide to simply treat the cancerous tumor with radiation or chemotherapy in hopes of slowing its growth.
But at the age of 76, some experts believe the senator's life expectancy could be less than a year.