Case Report: Extramedullary Hairy Cell Leukemia in Parotid Gland, Case Report and Review of the literature.

Hairy cell leukemia (HCL) presenting as extramedullary disease without bone marrow infiltration is extremely rare. We report a 42-year-old male diagnosed as extramedullary HCL in right parotid gland without cytopenia, bone marrow infiltration, and splenic involvement. Immunohistochemistry of core biopsy of was positive for LCA, CD 10, CD20, CD25, BCL2, BCL6, and cyclin D1, negative for CD3, and CD5 with Ki 67 of 10-15%. Molecular analysis showed BRAF V600E mutation. He was treated with Cladribine and 8 doses of weekly Rituximab without any local radiation. Post therapy, he had very good clinical and radiological improvement with complete resolution of parotid gland lesions with mild uptake in left scapula and right femoral epicondyle in PET CT scan. Key Words: hairy cell leukemia, parotid gland, extramedullary, without marrow involvement.