Highly aggressive ALK-positive anaplastic large cell lymphoma with a leukemic phase and multi-organ involvement: a report of three cases and a review of the literature.

Anaplastic large cell lymphoma (ALCL) is an aggressive neoplasm of T- or null cell phenotype and is recognized as a distinct clinicopathologic subtype of non-Hodgkin lymphoma (NHL) in the revised World Health Organization (WHO) classification of hematopoietic neoplasms. It is rarely associated with leukemic phase. Most cases with leukemic involvement are the small cell variant of ALCL. These cases often lack the pleomorphism seen in the common variant of ALCL and may be misdiagnosed. We report a series of three patients who presented with leukemic phase ALCL. The patients included an 11-year-old boy, a 29-year-old man, and a 59-year-old woman. The clinical and pathologic features of these cases are reviewed. The patients in our case series with leukemic phase ALCL exhibited rare clinical features. The patients presented with massive extranodal disease involving cerebrospinal fluid (CSF), liver, spleen, lungs, and bone marrow. CSF involvement was documented morphologically as well as by flow cytometry in two patients. Two of the patients had small cell variant and the third patient had common type ALCL. The neoplastic cells in all three patients were ALK positive; however these patients died within months of diagnosis. Leukemic phase ALCL is rare, and behaves in an aggressive manner. Some, but not all, cases in the literature presenting with peripheral blood involvement had small cell variant ALCL, as seen in two of our cases. The leukemic phase of ALCL should be considered when a T-cell leukemia with unusual morphologic features is encountered.