CD30(+) anaplastic large cell lymphoma: a review of its histopathologic, genetic, and clinical features

Anaplastic large cell lymphoma (ALCL) represents a generally recognized gro up of large cell lymphomas, Defining features consist of a proliferation of predominantly large lymphoid cells with strong expression of the cytokine receptor CD30 and a characteristic growth pattern. With the use of molecula r and clinical criteria, 3 entities of ALCL have been identified: primary s ystemic anaplastic lymphoma kinase (ALK)(+) ALCL, primary systemic ALK(-) A LCL, and primary cutaneous ALCL, ALK expression is caused by chromosomal tr anslocations, most commonly t(2;5). ALK(+) ALCL predominantly affects young male patients and, if treated with chemotherapy, has a favorable prognosis , It shows a broad morphologic spectrum, with the "common type," the small cell variant, and the lymphohistiocytic variant being most commonly observe d, The knowledge of the existence of these variants is essential in establi shing a correct diagnosis. ALK(-) ALCL occurs in older patients, affecting both genders equally and having an unfavorable prognosis. The morphology an d the immunophenotype of primary cutaneous ALCL show an overlap with that o f lymphomatoid papulosis, Both diseases have an excellent prognosis, and se condary systemic dissemination is only rarely observed. The described ALCL entities usually derive from cytotoxic T cells. In contrast, large B-cell l ymphomas with anaplastic morphology are believed to represent not a separat e entity but a morphologic variant of diffuse large B-cell lymphoma. Malign ant lymphomas with morphologic features of both Hodgkin disease and ALCL ha ve formerly been classified as Hodgkin-like ALCL. Recent immunohistologic s tudies, however, suggest that ALCLs Hodgkin-like represent either cases of tumor cell-rich classic Hodgkin disease or (less commonly)ALK(+) ALCL or AL K- ALCL, (C) 2000 by The American Society of Hematology.