Hairy Cell Leukaemia

Hairy Cell Leukaemia in an indolent B-cell malignancy driven by a BRAF V600E mutation. Although the typical patient is middle-aged with massive splenomegaly, pancytopenia and characteristic monocytopenia. They often get unusual infections - hairy cell  seems to be quite immunosuppresive. There is a preponderance towards men over women. In this case, the unfortunate patient was diagnosed when she was pregnant. She has been under the care of a haematologist for mild thrombocytopenia for some time - this got worse when pregnant, which triggered more investigations.

Bone marrow aspiration often gives a dry tap - this is because of bone marrow fibrosis. The hairy cells have oval nuclei and circumferential cytoplasmic hair-like projections. They are often quite rare on the blood film - here I have found a few examples (#1, #2, #3) but it's not as if there are hundreds. They have a characteristic immunophenotype of CD19+, CD20 bright, CD11c+, CD25+, CD103+, CD123+. Treatment can be with steroids and rituximab in a patient like this who is pregnant. Splenectomy can be tried in some patients, although newer drugs such as cladribine gives durable long term remissions.

Apart from the hairy cells, mild rouleaux (as this is a B cell malignancy) and any cytopenias, the rest of the film may show features of fibrosis if the patient has developed this. In this film, the patient hasn't.