A 70 year old Caucasian man presents for a routine yearly physical. He's been doing well, without problems, happy that he lost 15 lbs. without even trying over the last few months. Sure, he has a bit of fever and night sweats, but who doesn't? "At least it's not as bad as menopause," he says. He has a little fatigue, but it's just part of getting older, he thinks.
Exam shows cervical lymphadenopathy; you feel firm, round, discrete, mobile nodes. You might feel a spleen and a liver edge too. Routine CBC shows a leukocytosis, mild anemia, and mild thrombocytopenia. Here's the blood smear:
Challenge: What's your diagnosis?
First image shown under GNU Free Documentation License; second image shown under fair use.