This is hairy cell leukemia, which accounts for only 2% of all leukemias. Middle aged males are usually affected with splenomegaly and pancytopenia, but not lymphadenopathy. Some patients present with atypical mycobacterial infections. This disorder gets its name from the distinctive circulating B cells that have cell borders with small projections of blue cytoplasm. The nuclei are round to oblong with condensed chromatin. A characteristic feature is positive cytoplasmic staining for tartrate-resistant acid phosphatase (TRAP), seen here in the lower right panel. Chemotherapy can lead to remission in most cases.
| Our winner is: Sheetal Khandhar of OHSU School of Medicine, Portland, Oregon, USA
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