CD200 and B-cell chronic lymphocytic leukemia: CD200 expression is reported across most cancer types including hematologic malignancies such as acute myeloid leukemia (AML) [21], multiple myeloma (MM) [22], chronic lymphocytic leukemia (CLL) [23], and B-cell lymphoma [24]; solid tumors such as rectal [25], breast [26–27], colon [28–29], lung [30–31], ovarian [32], head and neck [33–34], glioma [35], pancreatic [36–37], and bladder [38]; and a variety of skin cancers including squamous cell carcinoma [39–41], basal cell carcinoma [42], Merkel cell carcinoma [43] and melanoma [32, 44–45].