Hairy cell leukemia: clinicopathological and immunophenotypic study.

Hairy cell leukemia (HCL) is a rare neoplasm of mature small B lymphoid cells with characteristic circumferential 'hairy projections' involving the peripheral blood, bone marrow and splenic red pulp. With the advent of immunophenotyping and newer treatment modalities, prolonged remission can be achieved after a definitive diagnosis. Due to the rarity of this condition and presence of only a few case series from India, this work was undertaken. The aim was to study the clinico-pathologic and immunophenotypic features of all cases diagnosed as hairy cell leukemia. The cases were retrieved from Hematopathology records, between 1991 and 2012. The complete clinical details, investigations, treatment and follow-up were obtained from Medical Oncology records. The peripheral blood picture, bone marrow cytology and trephine sections along with special stains were reviewed. There were 12 cases of HCL during the study period with a M:F ratio of 11:1. Of these, ten were diagnosed as classical HCL and two as variant HCL. The most common clinical manifestations were fever, easy fatigability and weakness. Splenomegaly was present in 81.8 % cases. Though all the patients showed some form of cytopenia, there were three (25 %) patients with leucocytosis. The smears from all patients showed atypical lymphoid cells with circumferential hairy projections. TRAP was positive in 9 patients (81.8 %). Immunophenotyping was done in six cases, four were confirmed as HCL and two were diagnosed as HCL-v. The patients treated with Cladribine generally had a good response. The characteristic morphology of the hairy cells; along with correlation with the clinical features, TRAP positivity and immunophenotyping by flow cytometry is essential for diagnosis. Treatment response with Cladribine is good and has prolonged remission rates.