Abstract: Objective : To investigate the clinicopathological and immunohistochemical characteristics of anaplastic large cell lymphoma (ALCL) and to compare the differences in clinical manifestation, treatment and prognosis between ALK-positive cases and ALK-negative cases. Methods : Histological and immunohistochemical staining methods (ABC method) were used to analyze 20 previously diagnosed cases of ALCL, and the correlated clinical data were reviewed. Results : Fifteen of the 20 cases were T/Null cell type (8 T and 7 Null) and were diagnosed as ALCL with immunohistochemistry. CD30 was strongly expressed in the 15 cases of ALCL. There were 9 ALK-positive cases. No correlation was found between ALK expression and sex, immunohistochemical type, histological type, or clinical stage. However, a significant correlation was found between ALK expression and age and sensitivity to chemotherapy (P <0.05). The remaining 5 cases were B cell type, and they were true DLBCL. Conclusion : Our study highlights the importance of histopathological features and the significance of CD30 and ALK in the diagnosis of ALCL. The differences between ALK-positive ALCL and ALK-negative ALCL suggest specific studies on these genes, including differences in clinical manifestation and remission rates after chemotherapy, should be performed.