Neuropathologists as well as surgical pathologists routinely evaluate CNS lesions from patients undergoing resection of a known metastasis for therapeutic reasons or from a patient with no known prior history of malignancy. The most common intracranial and intraspinal tumors are metastases (about 20%) and the incidence increases with age (Klos and O'Neill, 2004). The frequency of metastatic disease depends on the primary site, with lung, breast, skin (malignant melanoma), renal cell carcinoma, carcinoma of the gastrointestinal (GI) tract, particularly colon, and choriocarcinoma being the more common malignancies to involve the CNS in order of decreasing frequency. Four of these, lung, melanoma, renal cell and choriocarcinoma, are malignancies that tend to produce “hemorrhagic” foci (Mandybur, 1977). Hemorrhagic lesions should not automatically be considered more likely to be a metastasis, since some primary glial neoplasms can be abundantly hemorrhagic (Ragland et al., 1990).

In accordance with the most common types of systemic neoplasms in adults, the most common type of metastatic brain tumors are those that arise from lung cancers, the most common CNS metastases in men, and breast carcinoma, the most common metastases in women (Evans et al., 2004). Breast carcinomas, and others such as lung carcinoma inmen, are particularly prone tometastasize to the sella turcica and thereby become symptomatic by causing diabetes insipidus (Bobilev et al., 2005; Teears and Silverman, 1975; Yap et al., 1979).