Fig. 2. Trephine marrow sections from the case demonstrating diffuse sheets of small mature-looking lymphoid cells with round to mildly irregular nuclear outlines and abundant clear cytoplasm with a ‘fried egg’ pattern classical of hairy cell leukemia (A, Hematoxylin and eosin, ×400). On immunohistochemistry, these lymphoid cells show strong diffuse positivity for CD20 (B), CD11c (not shown), and CD10 (C, peroxidase-antiperoxidase, ×400).

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