Fig. 5
Spleen, lymph node and brain involvement by hairy cell leukemia-variant. a–d Hairy cell leukemia-variant diffusely infiltrates the red pulp of the spleen. Neoplastic cells display a fried egg appearance (a hematoxylin and eosin, ×200; b hematoxylin and eosin, ×1000). CD20 immunostain shows a diffuse replacement of the red pulp with scattered CD3-positive T-cells (c, d immunohistochemistry with hematoxylin counter stain, ×200). e–h Lymph node diffusely infiltrated by hairy cell leukemia-variant. The infiltrate is characterized by intermediate-sized lymphocytes with oval nuclei and moderately abundant clear cytoplasm, some of the leukemic cells show prominent nucleoli (arrowhead) (e hematoxylin and eosin, ×200; f hematoxylin and eosin, ×1000). Hairy cell leukemia-variant cells highlighted by immunohistochemical B-cell marker CD20 admixed with background small CD3-positive T-cells. (g, h immunohistochemistry with hematoxylin counter stain, ×200). i–k Involvement of the brain by hairy cell leukemia-variant (case #3): Multiple brain lesions by MRI (i). Brain biopsy specimen showing brain parenchyma with hemorrhages resembling blood lakes containing atypical lymphocytes (j hematoxylin and eosin, ×100). High-power showing blastoid morphology of hairy cell leukemia-variant cells highlighted by CD20 (inset) (k hematoxylin and eosin, ×400)
