Case report:

A 52 year gentleman came to emergency department with complaints of fatigue and generalized malaise for one month and left sided abdominal pain since 2 weeks. On examination he had massive splenomegaly and no lymphadenopathy. He was initially evaluated for the baseline routine blood investigations. His Hemoglobin 6.9gm/dl, Total WBC count -9.46 thou/µL and platelet count -30thou/µL. Serum creatinine was mildly elevated 1.67mg/dl. Serology for Hepatitis B surface antigen reactive. Serum uric acid mildly elevated with -8.0mg/L. B2 microglobulin levels also elevated with 5065ng/ml.

Peripheral smear examination showed pancytopenia with increase in atypical lymphoid cells (65%) with round to oval nucleus, moderate amount of basophilic cytoplasm with fuzzy cytoplasmic borders and circumferential hairy projections. Features of chronic lymphoproliferative disorder was suggested and advised bone marrow and flowcytometry Immunophenotyping.

Bone marrow aspirate was a dry tap which is inadequate for opinion.

Bone marrow biopsy showed a patchily hypercellular marrow with evidence of interstitial infiltration by small to medium monotonous sheets of lymphoid cells replacing the marrow spaces with pericellular vacuolations resembling “fried egg appearance”. Reticulin stain highlighted the grade I to II pericellular fibrosis. A diagnosis of hairy cell leukaemia was considered.

Flow cytometry Immunophenotyping done on the peripheral blood with 65% atypical cells  showed a population of B cells which expressed CD20, CD200, CD49d, CD123, CD103, CD25, CD11c and showed Kappa light chain restriction. Other markers of T cell differentiation were negative. Based on the classic immunophenotype and morphology a conclusive diagnosis of Hairy cell leukaemia was made.

Molecular studies of the DNA was done on the bone marrow biopsy tissue by Real time PCR and BRAF 600 mutation was detected. 

Summary

Hairy cell leukemia though rare indolent neoplasm, has  unique characteristics in clinical presentation and diagnostic features and thorough examination of peripheral smear gives definitive clue to the diagnosis confirmation by Immunophenotyping and bone marrow histo-morphology. Although many lymphoid neoplasms like SMZL, SDRPL, HCL-variant can present with hairy like cells in peripheral blood it’s important to differentiate them and guide them for a correct diagnosis. This case highlights the importance of morphology along with confirmation with other diagnostic modalities.