The problem of anaplastic large cell lymphoma (ALCL) is extensively re
viewed by depicting the clinical, pathological and biological characte
ristics of the four main varieties of ALCL: common, Hodgkin's like/Hod
gkin-related, lympho-histiocytic, and giant-cell rich. Special emphasi
s is given to the differential diagnosis between ALCL Hodgkin like and
Hodgkin's disease in the light of possible therapeutical differences.