Anaplastic large cell lymphoma in leukemic phase: Extraordinarily high white blood cell count

Anaplastic large cell lymphoma (ALCL) is a distinct type of T/null‐cell non‐Hodgkin lymphoma that commonly involves nodal and extranodal sites. The World Health Organization of lymphoid neoplasms recognizes two types: anaplastic lymphoma kinase (ALK) positive or ALK negative, the former as a result of abnormalities involving the ALK gene at chromosome 2p23. Patients with ALCL rarely develop a leukemic phase of disease, either at the time of initial presentation or during the clinical course. Described herein is a patient with ALK+ ALCL, small cell variant, associated with the t(2;5)(p23;q35), who initially presented with leukemic involvement and an extraordinarily high leukocyte count of 529 × 109/L, which subsequently peaked at 587 × 109/L. Despite chemotherapy the patient died 2½ months after diagnosis. In the literature review 20 well‐documented cases are identified of ALCL in leukemic phase reported previously, with a WBC ranging from 15 to 151 × 109/L. Leukemic phase of ALCL occurs almost exclusively in patients with ALK+ ALCL, most often associated with the small cell variant and the t(2;5)(p23;q35), similar to the present case. Patients with leukemic phase ALK+ ALCL appear to have a poorer prognosis than most patients with ALK+ ALCL.