3.28 Trompe L'Oeil Not Only in Painting: CLL Concomitant with Hairy Cell Leukemia is Not Rare
The coexistence of chronic lymphocytic leukemia (CLL) and hairy cell leukemia (HCL) has already been reported in the literature, but as an exceedingly rare event, because the presentation (clinical and laboratory) is generally CLL-like and HCL is discovered ‘by the way’. To prove that the concomitance between these two diseases is not as rare as previously believed, we have to think ‘semantically’: the question is not how many CLL cases are concomitant with HCL, but how many HCL cases are concomitant with CLL. CLL originates from antigen-stimulated mature B lymphocytes and is the most common type of leukemia in older adults, accounting for 25% of all leukemia cases. HCL is also a chronic lymphoproliferative disorder originating from mature B lymphocytes. HCL accounts for 2-3% of all leukemia cases. The male to female ratio is approximately 4:1. The etiology is not known. CLL and HCL have distinct clinical, morphological and immunophenotyping features. The occurrence of second neoplasm, especially non-Hodgkin’s lymphomas, is well known in HCL patients. In the past 10 years we have diagnosed in our hemato-oncologic clinic 22 cases of HCL, 4 of them (18% of all cases of HCL diagnosed during this period) concomitant with CLL. We did not perform immunoglobulin gene rearrangement analysis, so we cannot know whether the origin is from different B cell clones or not; we can only affirm that the same light chain type was present on the membranes of both CLL and HCL cells. All cases of lymphoproliferative disorders (LPD) are systematically screened in our lab for the presence of an additional monoclonal B-cell population. Conclusion: the concept that concomitant CLL and HCL is a rare event is challenged. It is a mere ‘trompe l’oeil’, due to the rarity of HCL.