Abstract: Objective: To discuss the application of thinlayer cytology (TLC) smears and immunocytochemistry(ICC) in identifying the cell types of malignant tumors. Methods: ICC was performed with 21 types of antibodies in 130fine needle aspiration (FNA) specimens to identify the types of malignant tumor cells. Results: The cell types of 43 of the56 poorly differentiated carcinoma specimens identified by ICC were consistent with those identified by histopathology re-sults, providing an accuracy rate for ICC of 76.8% for these samples. The cell types of 46 of the 47 specimens suspectedas nonHodgins lymphomas(NHL) or small cell cancer identified by ICC were accordant with histopathological results. Theaccuracy rate of ICC for these samples was 97.9%. The cell types of the 27 specimens with unknown histological originwere 100% accurately identified by ICC. The results of cytospin in 19 of the 20 cases were in accordance with those ofTLC. The ICC results in mesenchymal tumors and lymphoma could be easily differentiated, while falsepositives could of-ten be seen in smears with cancer nests. Conclusion: ICC and TLC smears can be applied to identify the cell types of ma-lignant tumors, with a satisfactory accordance rate compared to histological results. Diagnosis using fine needle aspirationbiopsies can provide valuable information for clinical treatment.