The FDA (the U.S. Food and Drug Administration) has not approved lenalidomide for this specific disease, but it has been approved for other uses, including for patients with multiple myeloma and some patients with myelodysplastic syndrome. This treatment is investigational because it is not approved by the FDA for patients with AML. Lenalidomide is a chemotherapy that also modulates the immune system, and is in a category of drugs called immunomodulatory drugs or IMIDs. Some research studies suggest that lenalidomide may be effective in patients with AML. Since the investigators know that many patients who receive MEC chemotherapy alone have less than desired response rates and overall shorter periods of remission (time free from leukemia) after treatment, the investigators are studying whether the addition of lenalidomide to MEC improves upon typical responses.