Clonality as a criterion in the differential diagnosis of chronic neutrophilic leukaemia

Chronic neutrophilic leukaemia (CNL) is a rare BCR/ABL negative myeloproliferative disorder of elderly patients, showing sustained neutrophilia and splenomegaly. Differentiation between CNL and leukaemoid reactions (LR) is problematic since both conditions share similar morphological features but is essential because CNL patients generally have a poor prognosis. We studied blood samples from 10 female patients with CNL or LR using the HUMARA assay to determine clonality patterns in neutrophils. T-lymphocytes of the patients were investigated as an internal control cell population. In all five CNL patients the neutrophils, and in four of them also T-lymphocytes were monoclonal, indicating that the latter may also originate from the neoplastic clone. In LR patients the neutrophils and T-lymphocytes were generally polyclonal except in one patient showing monoclonal neutrophils suggesting that this patient might be in the process of developing a myeloproliferative disorder. In females clonality studies of blood neutrophils using HUMARA aid in distinguishing patients with monoclonal CNL from polyclonal LR.