Cerebrospinal fluid ferritin in malignant CNS involvement.

Cerebrospinal fluid (CSF) ferritin was measured in patients with benign inflammatory and noninflammatory neurologic disorders and in patients with malignant disease with and without documented central nervous system (CNS) involvement. CSF ferritin levels were increased in the majority of patients with inflammatory neurologic disease and in patients with malignant involvement of the CNS. In contrast, in patients with noninflammatory neurologic disorders and in malignant disease without CNS involvement, CSF ferritin levels were normal. These findings indicate that although the specificity of CSF ferritin measurement is limited, it is a highly sensitive test that may be useful in the initial evaluation of patients with malignant CNS involvement, and in assessing their response to therapy.