Leukemic presentation of ALK-positive anaplastic large cell lymphoma in an adult patient with hemophagocytic lymphohistiocytosis

Systemic ALK + anaplastic large cell lymphoma (ALCL) is a CD30-positive T cell neoplasm that commonly affects lymph nodes with frequent involvement of extranodal sites. A leukemic phase with peripheral blood involvement is extremely rare, and therefore, recognition of this uncommon phenomenon is crucial to avoid misdiagnosis and delayed treatment. We report a case of a previously healthy adult patient who presented with peripheralizing ALK-positive ALCL accompanied by hemophagocytic lymphohistiocytosis (HLH). Comprehensive ancillary studies were essential for establishing the diagnosis and determining blood involvement.