Biologic characteristics of breast cancer detected by mammography and by palpation in a screening program: a pilot study.

OBJECTIVE

To compare the histopathologic features and expression of p53 and c-erb B2 in the tumours detected by mammography only (clinically occult tumours) and the tumours detected by a nurse examiner (clinically palpable tumours).

SETTING

London branch of the Ontario Breast Screening Program, which uses both clinical breast examination and mammography as screening methods.

INTERVENTIONS: Pathologic review and immunohistochemical staining of all tumours detected between 1990 and 1993.

OUTCOME MEASURES: Categorization of tumours by detection method and analysis of tumour size, grade, type, lymph node status and c-erb B2 and p53 expression in each group.

RESULTS

From 1990 to 1993, 131 tumours were detected in patients ranging in age from 50 to 85 years (median 63 years). Sixty-seven occult tumours and 64 palpable lesions were detected. The occult tumours were significantly smaller (1.34 cm v. 2.29 cm, p < 0.0001) than the palpable ones and included a higher proportion of special-type lesions and ductal carcinoma in situ (43.3% v. 10.9%, p < 0.0001). Occult invasive carcinomas were of lower grade than palpable carcinomas (68.4% grade 1, 21.1% grade 2, 10.5% grade 3 v. 32.8% grade 1, 36.1% grade 2, 31.1% grade 3, p < 0.0001). Fewer occult lesions showed axillary nodal metastases (19.6% v. 40.6%, p = 0.02). No statistically significant differences were found for p53 or c-erb B2 positivity between the 2 groups.

CONCLUSION

Tumours detected by different screening methods in a screening program have different pathologic characteristics.