ALK positive lymphohistiocytic variant of anaplastic large cell lymphoma in an adult.

The lymphohistiocytic (LH) variant of anaplastic large cell lymphoma (ALCL) has, for a long time, been considered typical of children and adolescents. The aim of this study is a detailed characterization of a case of this peculiar ALCL subtype affecting an adult patient. DESIGN AND METHODS: A 36-year old male presented with diffuse adenopathy and systemic symptoms (high fever, anorexia, asthenia); a diagnosis of CD30+/ALK+ ALCL, LH variant, was morphologically suspected and corroborated by immunohistochemistry that was crucial for the definitive diagnosis and subtyping. RESULTS: The neoplastic population consisted of cells highly variable in size and shape but more often isolated and largely obscured by a predominant reactive cellular infiltrate of histiocytes and plasma cells. The lymphoma cells exhibited a null non-B non-T antigenic profile, but reacted strongly for the Ber-H2/CD30, EMA, ALKc anti-TIA-1 monoclonal antibodies. The patient underwent chemotherapy plus bone marrow transplantation and, one year after diagnosis, he is well and in complete remission. INTERPRETATION AND CONCLUSIONS: Our findings provide additional evidence that: a) ALK+ lymphoma represents a single disease with a broad spectrum of morphology; b) clinicians and pathologists should be aware of the possible occurrence of LH variant of ALK+ ALCL also in adults in whom a favorable response to therapy may be expected despite systemic disease and an aggressive clinical presentation.