Mammographically detected breast cancer. Nonpalpable is not a synonym for inconsequential

Needle-guided breast biopsy has become a regularly recommended procedure to excise nonpalpable, questionable breast lesions detected by mammography. Whether cancers detected in this manner have a more favorable outcome than those detected by clinical examination is not clearly documented.

To address questions about the biology of mammographically detected cancer and likelihood of axillary node metastasis, as well as the accuracy of screening mammography, data from 3752 needle-guided breast biopsies and 1175 nonpalpable breast cancers were reviewed.

Between 1974 and 1992, 3752 needle-guided biopsies were performed in 3441 women for nonpalpable breast lesions. Benign disease was disclosed in 2575 (68.7%) biopsies and malignancy in 1175 (31.3%). Of 1130 malignancies, 61.8% were invasive carcinomas; 4.8% were microinvasive ductal carcinomas; 28.5% were ductal carcinomas in situ; and 4.8% were lobular carcinomas in situ. Axillary dissection in 558 patients with invasive carcinoma revealed that 27.1% had at least one positive axillary node. Of patients with invasive cancers presenting as nonpalpable calcifications alone, 27.5% had at least one positive axillary node.

More than one fourth of patients with nonpalpable, invasive cancer in this series had axillary node metastasis. Therefore, axillary dissection is an important treatment consideration for all patients with invasive carcinoma, despite technique of detection. Ductal carcinomas in situ detected as limited calcifications do not require axillary dissection. In this study, 31% of biopsies proved the presence of malignancy, an acceptable and appropriate benign-to-malignant ratio.