The safest course is tissue or cytologic biopsy evaluation of all dominant masses found on physical examination and, in the absence of a mass, evaluation of suspicious lesions shown by breast imaging. Over 1 million women have breast biopsies each year in the United States. Between 70% and 80% of these biopsies yield a benign lesion (64). The diagnosis of a benign breast lesion versus breast cancer is often difficult to determine based on clinical examination and requires evaluation of tissue by fine needle aspiration cytology (FNAC), core needle biopsy (CNB), or excisional biopsy (EB). Both FNAC and CNB are reasonable techniques for the evaluation of a palpable or image-identified lesion. CNB evolved as the diagnostic procedure of choice. More than half of all breast biopsies use a core-needle technique. The sensitivity of CNBs performed using either stereotactic or ultrasound guidance is 97% to 99% (65). CNB is used increasingly to diagnose breast cancer and to determine tumor histology, grade, and marker expression; select neoadjuvant therapy; and predict sentinel lymph node status (66). CNB and fine needle aspiration (FNA) are less invasive and achieve better cosmesis than excisional or even incisional biopsy. The main limitations of FNA are high rate of insufficient sampling and inability to distinguish invasive from noninvasive cancers. CNB is a well-accepted alternative to surgical biopsy and can avoid surgical biopsies in most patients (67). Investigators of the Fifth Radiologic Diagnostic Oncology Group demonstrated that image-guided biopsy of breast lesions provides high diagnostic accuracy. The sensitivity, specificity, and accuracy of CNB were 0.91, 1.00, and 0.98, respectively (68).
About 30% of lesions suspected to be cancer prove on biopsy to be benign, and about 15% of lesions believed to be benign prove to be malignant (23). Dominant masses or suspicious nonpalpable breast lesions require histopathological examination. Histologic or cytologic diagnosis should be obtained before the decision is made to monitor a breast mass (69). An exception may be a premenopausal woman with a nonsuspicious mass presumed to be fibrocystic disease. An apparently fibrocystic lesion that does not completely resolve within several menstrual cycles should be sampled for biopsy. Any mass in a post-menopausal woman who is not taking estrogen therapy should be presumed to be malignant. Some clinicians will monitor a mass when results of the clinical diagnosis, breast imaging studies, and cytologic studies are all in agreement, such as with fibroadenoma. Many clinicians will not leave a dominant mass in the breast even when FNAC or CNB results are negative, unless the FNA or CNB shows fibroadenoma. Such cases require periodic follow-up. Some surgeons excise lesions when the sampling technique shows only fibrocystic disease. Figures 21.4 and 21.5 present algorithms for management of breast masses in premenopausal and postmenopausal patients. Simultaneous evaluation of a breast mass using clinical breast examination, radiography, and needle biopsy can lower the risk of missing cancer to only 1%, effectively reducing the rate of diagnostic failure and increasing the quality of patient care (70).