Anaplastic large-cell lymphoma with rapid evolution to leukemic phase

Anaplastic large-cell lymphoma (ALCL) is a lymphoproliferative disorder tha t frequently presents with disseminated disease and extranodal involvement. Rare atypical cells have been detected in the peripheral blood in occasion al cases. However, the presence of a prominent leukemic phase is extremely rare in these patients. We describe a patient with a small-cell variant of ALCL of T-cell phenotype, ALK-1 positive, who developed a rapid leukemic ph ase in association with the progression of the disease. Similar to the noda l biopsy, the predominant cells in bone marrow and peripheral blood were sm all atypical lymphoid cells. The large tumor cells expressed ALK immunoreac tivity with a cytoplasmic and nuclear pattern, whereas some of the small ce lls showed only a nuclear-restricted pattern of staining. An RT-PCR study d etected the NPM-ALK chimeric product in the nodal biopsy and in a periphera l blood sample in the early phase of the disease. but it became negative in a peripheral blood sample obtained after completion of the chemotherapy tr eatment, suggesting that this assay may be useful in the follow-up of these patients. This case indicates that a prominent leukemic phase may develop in ALCL as a manifestation of tumor dissemination and that it may be compos ed of a predominant small-cell atypical component.