Metastasis

Definition

Metastasis refers to the spread of cancer from a primary neoplasm. Metastasis results because cancer cells have broken away from a neoplastic malignancy from an original organ site and have spread to another site. Intracranial brain metastases occur through blood circulation. Metastases are well demarcated by round lesions at the gray–white junction (Khosla 2007). Metastatic tumor cells are similar to those of the primary malignancy, which is defined by the type of cells from which the cancer originated. The rate of metastasis increases when the primary tumor is not controlled, and relapsing tumors are more likely to produce metastasis than the primary tumor (Leibel 1994). Metastases from lung cause shorter survival rates than metastases from prostate or breast primaries (Rubin and Scarantino 1994). Brain metastases are typically treated with whole brain radiotherapy and stereotactic radiosurgery. Proton beam therapy is being applied to metastases in some organs, but is not...