Objective: To study the clinical significance and expression of p53

C-erbB-2 and PCNA in bronchioloaveolar carcinoma (BAC). Methods: Thirty-six cases of BAC were collected (25 cases localized type and 11 cases diffused type).The expression of p53

C-erbB-2 and PCNA in BAC tissues was determined with immunohistochemical methods. Results: The positive rate of p53 gene protein expression and PCNA proliferating index in the diffused type were 81.82% and 72.23±8.59 respectively

which were both significantly higher than 36.00% and 46.14±6.20 of those in the localized type ( P< 0.05);there was no significant difference on C-erbB-2 in the localized type and diffused type;the positive expression of p53 and PCNA was significantly related to the lymph node metastasis

and PCNA proliferating index was closely related to the P-TNM staging ( P <0.05).The lymph node numbers and positive rate (2.63

72.73%) of the diffused type with the lymph node metastasis were higher than those (2.0

52.0%) in the localized type and the positive expression of p53

C-erbB-2 gene protein were more severe than the localized type with or not. Conclusion: The expression of p53and PCNA could be quite valuable in the prognostic evaluation of BAC and the diffuse BAC could possess more biological characteristics of the malignant tumor.