The tumor microenvironment in hairy cell leukemia (HCL) and splenic B cell lymphoma with prominent nucleoli (SBLPN).

Hairy cell leukemia (HCL) is an indolent B-cell malignancy characterized by distinctive morphologic features (hairy cytoplasmatic protrusions'hairy cells', HCs), cytopenia, and splenomegaly. Classical HCL is characterized by the BRAFV600E mutation. Splenic B-Cell Lymphoma with Prominent Nucleoli (SBLPN) - previously known as HCL variant - lacks the BRAFV600E mutation and shows a more aggressive clinical course. Current treatment approaches achieve remission rates above 95%, but high relapse rates highlight the necessity for tailored strategies. The unique dissemination profile of HCs into bone marrow, spleen, and blood, and their unusually low abundance in lymph nodes, indicates that HCs must have a particular interaction capacity with accessory cells and matrix proteins. However, the micro environmental interactions of HCs are incompletely understood. This review highlights the interaction between HCs and the tumor microenvironment, including T-cell dysfunction and hematopoietic inhibition due to cytokine production and bone marrow fibrosis, playing a crucial role in disease progression.