Which Cytochemical stain is used in diagnosing hair cell leukemia?

Tartrate-resistant acid phosphatase (TRAP) is a specific cytochemical stain that is particularly associated with hairy cell leukemia. This condition is characterized by the presence of abnormal B lymphocytes with hair-like projections, and TRAP is used to highlight this abnormality.

When a sample is stained with TRAP, hairy cells demonstrate increased enzyme activity, which is not inhibited by tartrate. This unique property helps in differentiating hairy cell leukemia from other hematological malignancies and confirms the diagnosis.

Other stains mentioned, while useful in different contexts, do not have the specificity that TRAP has for hairy cell leukemia. For instance, acid phosphatase is a more general marker and may show activity in several types of leukemias, while Sudan Black B is primarily used for differentiating myeloid cells, and peroxidase stains are typically associated with granulocytes. Thus, the specificity of the tartrate-resistant acid phosphatase stain makes it the preferred choice for diagnosing hairy cell leukemia.