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Biologic characteristics of breast cancer detected by mammography and by palpation in a screening program: a pilot
E Tweedie1, K Tonkin, N Kerkvliet
1Department of Pathology, London Health Sciences Centre, Ont.
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.