Schematic representation of ALCL entities and their genetic-associated aberrations. ALK-positive ALCL is a well-delineated entity, primarily defined by ALK translocations. Other lymphomas with similar anaplastic morphology and CD30 expression do occur, either as a systemic disease, referred as ALK-negative ALCL, a provisional entity in the current classification, or as a primary cutaneous neoplasm, primary cutaneous ALCL, which are part of the spectrum of primary cutaneous CD30⁺ lymphoproliferative disorders and usually pursue a benign course. sALCL, systemic ALCL; rear., rearrangement.