目的　探讨 DNA倍体及细胞增殖活性在肿瘤诊断上的价值。方法　采用流式细胞术检测 32例乳腺肿瘤细胞DNA含量和细胞周期。结果　乳腺癌的异倍体率高达 70 % ,纤维腺瘤均为二倍体 ,乳腺癌细胞的 DNA指数 (DI)与纤维腺瘤的 DI有显著差异 (P<0 .0 1 ) ;细胞周期分析发现乳腺癌增殖活性 (S期百分比或增殖指数 ,PI)明显高于纤维腺瘤 (P<0 .0 1 ) ;乳腺癌 DI随肿瘤组织学分级的增高而增高 (P<0 .0 5 ) ;腋淋巴结有转移组 DI、PI高于无转移组 ,但无统计学意义。结论　异倍体及高增殖活性在乳腺良恶性肿瘤鉴别诊断中具有很重要的意义。 Objective To investigate the value of DNA ploidy and cell proliferation activity in the diagnosis of tumors. Methods Flow cytometry was used to detect the DNA content and cell cycle of breast cancer cells in 32 cases. Results The aneuploidy rate of breast cancer was as high as 70%. Fibroadenoma was diploid. The DNA index (DI) of breast cancer cells was significantly different from that of fibroadenoma (P<0.01); It was found that breast cancer proliferation activity (Percent S phase or proliferation index, PI) was significantly higher than that of fibroadenomas (P<0.01); Breast cancer DI increased with the increase of tumor histological grade (P<0.05). ); axillary lymph node metastasis group DI, PI higher than no metastasis group, but no statistical significance. Conclusion Aneuploidy and high proliferative activity play an important role in the differential diagnosis of benign and malignant breast tumors.