Severiano Ballesteros' brain tumor is cancerous and he will undergo another operation to relieve pressure caused by swelling and bleeding that have recently developed, according to the . The remaining parts of the malignant tumor, located in a very deep part of the brain, will be removed in Friday's procedure. Based on an analysis of cells already moved, the tumor is classified as an oligoastrocytoma, a type that affects "cells that cover and protect the nerve cells in the brain and spinal cord," the hospital said.
Ballesteros was admitted to the hospital Oct. 6, and 10 days later, a sizable part of the tumor was taken out. Part of his skull was removed -- a procedure known as decompressive craniotomy -- to allow room for a swelling brain to expand. Doctors said it was not uncommon after such complex operations. Ballesteros, who won three British Opens and two Masters, briefly lost consciousness while at Madrid's international airport on Oct. 6 and was admitted to the hospital. Ballesteros, who won a record 50 tournaments on the European Tour, retired last year because of a long history of back pain and has since concentrated on golf course design.