Gliomatosis cerebri (GC) is defined by the World Health Organization as a neoplasm of the glial cells. It is extremely rare, and there exists only 160 documented cases since 1897. There is no known treatment and the median survival rate is one year. The association of extracranial and CNS tumors is unusual, only three cases of breast cancer have been associated with gliomas and meningiomas but none with GC. Below we describe a case of breast cancer associated with GC and review the anatomoclinical and radiological manifestations of Gliomatosis Cerebri.