PMC5419203_01
(A) Larger lymphoid cells/hairy cells in bone marrow aspirate smear (May-Grunwald Giemsa stain, x1000); (B) Trephine biopsy showing interstitial infiltrate of hairy cell having a typical "fried egg" appearance (Hematoxylin and Eosin stain, x600); (C) Immunohistochemistry for DBA.44 highlights hairy cells (Hematoxylin counterstain, x600); (D) Immunohistochemistry for mast cell tryptase highlights mast cells (Hematoxylin counterstain, x600). (E) ARMS-PCR and agarose gel electrophoresis showing positivity for BRAF V600E mutation (lane 3); 100bp ladder (lane 1), positive control (lane 2), and negative control (lane 4).
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A few cells had grooved/reniform nucleus or cytoplasmic projections (Figure 1A). Trephine biopsy showed an interstitial infiltrate, typical of hairy cell leukemia (Figure 1B, C) along with an increase in mast cells confirmed by mast cell tryptase immunohistochemistry (Figure 1D). A diagnosis of hairy cell leukemia with atypical features (CD19 negative subclone, CD10 positivity, reactive plasmacytosis and mast cell hyperplasia) was made which was subsequently confirmed by amplification-refractory mutation system polymerase-chain-reaction (ARMS-PCR) for BRAF V600E mutation (Figure 1E).
Multiparametric flow cytometry shows two distinct clones (CD19pos and CD19neg) of cells both of which are positive for CD45, CD22, CD10, CD25, CD103, CD11c, CD123 and surface Igkappa in similar intensities. The plasma cells do not show clonal restriction.
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Multiparametric flow cytometry (Figure 2) was performed on the BMA using four/six color antibody panels by lyse-wash-stain method (antibodies from BD Biosciences, San Jose, CA). The plasma cells (CD38pos/CD138pos/CD19pos/CD81pos/CD56neg and no light chain restriction - Figure 2) and mast cells (CD117pos/CD33pos/CD2neg/CD25neg) showed normal immunophenotype indicating reactive plasmacytosis and mast cell hyperplasia.