*6.9.1 Morphology and immunophenotype*

On routine peripheral blood smears, the cells have round, oblong, or reniform nuclei and moderate amounts of pale blue cytoplasm with thread-like or bleb-like extensions. On bone marrow aspiration the cells cannot be aspirated and gives "dry tap", Bone marrow biopsy shows diffuse interstitial infiltrate of tumor cells enmeshed in an extracellular matrix composed of reticulin fibrils giving fried egg appearance. Spleen appears beefy red on gross appearance. Microscopy shows heavily infiltrated splenic red pulp leading to obliteration of white pulp.

The classic immunophenotypic profile of HCL consists of bright monotypic surface immunoglobulin, bright coexpression of CD20, CD22 and CD11c, and expression of CD103, CD25, CD123, T-bet, Annexin A1 (ANXA1), DBA.44 (CD72), FMC-7 and cyclin D1 (usually weak) [1, 25].
