Historical Background of Hairy Cell Leukemia

Hairy cell leukemia (HCL) is an uncommon but distinct form of chronic B-lymphoproliferative disorders characterized by an indolent course, peripheral cytopenias and splenomegaly due to the presence of characteristic neoplastic B lymphocytes in the blood, bone marrow and organs of the"classic" reticuloendothelial system (RES), associated with reticulin-fibrosis of the marrow.The diagnosis is based upon the recognition of the characteristic "hairy" nature of the leukemic lymphoid cells in theperipheral blood smears and the typical appearance and pattern of infiltration in the bone marrow biopsies in association with increased reticulin and eventual fibrosis of the marrow.

Additional special features include the presence of tartrate resistant acid phosphatase (TRAP) positivity within the cells associated with a specific HCL immunophenotypic profile on flow cytometry and elevated levels of soluble interleukin 2 receptors (solIL-2R) in the peripheral circulation, which are all important features inestablishing the diagnosis.

Historically HCL was initially recognized in 1923 by Ewald who described it as leukamische reticuloendotheliose . Other terms, such as leukemic reticuloendotheliosis, histiocytic leukemia, malignant reticulosis, and lymphoid myelofibrosis had all been used.

However, Bouroncle et al. were the first group to describe HCL as a distinct clinical and histopathologic entity in 1958, identifying it as a disorder with an indolent course, characteristic clinical and laboratory features and an excellent prognosis if treated correctly. The beneficial effect of splenectomy had already been noted in earlier reports, yet nomenclature remained problematic and confusing, while no progress was made at that time in terms of identifying the true nature of the neoplastic cells, until the newer immunophenotypic methodologies became available in the mid-1970's.

In 1969, Lee et al also described 26 HCL patients, still using the terminology of reticulum cell leukemia, stressing its similarity to chronic lymphocytic leukemia (CLL). In 1966, Schrek and Donnelly were the first to use the term "hairy cell" (HC), noting the fine hair-like cytoplasmic projections under contrast phase microscopy and realizing that their two cases were similar to those described earlier in 1958.

Thereafter, the terms HC and HCL were used widely and, once the era of modern immunology developed and immunophenotyping using flow cytometry and FACS became routine procedures, more groups became interested in the true nature and identification of HC and HCL by surface markers, transmission and scanning electron (and immunoelectron) microscopy.

Brought to you by Sayed EL Assal who is a physician graduated from faculty of medicine 7 years ago and since then he's working in health field.

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