Primary tumors of other organ systems do metastasize in. Most tumors metastasize to the lung before proceeding to the brain. Breast, prostate, melanoma, and kidney tumors are exceptions to this rule. Breast and prostate tumors metastasize to the dura and not to the brain. Melanomas and Kidney tumors metastasize to the brain directly.
Melanomas have the greatest likelihood of getting to the central nervous system.
In contrast, kidney tumors often do not appear in the brain until years after the primary lesion. Often, they appear as multiple ball shaped lesions. In some cases, there is severe hemorrhage which increases the mass of the tumor and causes herniation. This tumor hones to CNS although no one understands why. With the rise of AIDS cases, this type of tumor has become very common.