Nonpalpable breast cancer: needle-localized biopsy for diagnosis and considerations for treatment.
Screening mammography as an adjunct to physical examination led to the discovery of 237 radiographically suspicious but nonpalpable breast lesions. Needle localization of the lesion preoperatively in the mammography suite followed by breast biopsy led to the diagnosis of 64 nonpalpable carcinomas, including 25 invasive, 16 minimally invasive, and 23 noninvasive cancers. Noninvasive and minimally invasive cancers were microscopic. Of the invasive lesions, 7 were 10 mm or less in diameter and 14 were 11 to 20 mm in diameter. Noninvasive and minimally invasive cancers tended to occur in younger women (average age 52 and 51 years, respectively), and almost uniformly appeared as clustered calcifications mammographically. Invasive cancers affected an older population (average age 65 years), and the mammographic appearance was that of a mass in the majority of cases. A variety of surgical procedures were carried out subsequent to biopsy to provide definite treatment of these nonpalpable breast cancers. A review of surgical specimens available from these procedures demonstrated a 27 percent incidence of residual disease at the biopsy site. In patients who underwent mastectomy, 34 percent had an unsuspected focus of cancer in another quadrant of the breast and an additional 14 percent had an unsuspected focus of epithelial atypia. No patient with either noninvasive or minimally invasive cancer was found to have axillary lymph node metastases. Twenty-nine percent of patients with invasive tumors demonstrated lymph node metastases in the axilla. Our results demonstrate the efficacy of preoperative needle localization to assist in the biopsy of nonpalpable breast lesions and the diagnosis of a significant number of early breast cancers. The treatment plan for patients with these cancers must address the high incidence of residual disease at the biopsy site, multicentricity, and the proved capacity for invasive lesions to metastasize to the axillary lymph nodes, regardless of the size of the primary tumor.