During Cycle 1 the participant will come into clinic every week. At each visit, the participant will have a physical exam and will be asked questions regarding general health and specific questions about any problems that the participant might be having with any medications. About 2-3 additional tablespoons of blood will be taken before the participant's begins ruxolitinib, on Cycle 2 Day 1, Cycle 3 Day 1, and at the end of the study for research blood tests. Because these tests are being performed for research, and their clinical usefulness is unknown, the participant will not receive the results of these tests. The investigator will assess the participant's tumor by CT scans or MRI every 2 cycles. In addition, if the participant has tumors that are visible or can be palpated (felt), then they will be measured by the participant's study doctor in the clinic. If the participant has had a history of cancer in the bones or suspected cancer in the bones, then a bone scan will be performed before the participant can begin ruxolitinib. The bone scan may be repeated every 2 cycles and at the end of the study if the participant study doctor believes it is clinically needed. Otherwise, it does not need to be repeated. Photographs may be taken of the participant's tumor to assess the tumor response to the treatment.