What Causes Anemia Along With Excessive Weight Loss And Night Sweats?

My dad is anemic. His hemoglobin runs between 8.5 and 9. His CRP is 94 and his SED rate is 110. There was also a test done that showed his red blood cells are mildly stacking like coins. So far they have not been able to determine the cause. He lost 15 lbs in about 30 days. He has no appetite. He is not losing weight at this point because he is drinking Ensure Plus for meal supplements. He also has night sweats, but it does not soak his sheets. Can you give us any idea what could be wrong?