The FR is an emerging therapeutic target for diagnosis and treatment of cancer and chronic inflammatory diseases. Expression of the FR is selectively upregulated on certain malignant cells[10] and activated macrophages.[11] Overexpression of the FR on these types of cells is clinically significant because they designate areas where the physiological symptoms of disease are most extensive. The malignant cells indicate the presence of tumors associated with ovarian, lung, breast, kidney, brain, endometrial, and colon cancer.[12] Macrophages become activated in chronic diseases such as rheumatoid arthritis, Crohn's disease, ulcerative colitis, psoriasis, atherosclerosis, diabetes, and most other inflammatory diseases.[12]