A surgeon is often asked to see a patient after the finding of a palpable breast mass, or because of a concerning finding on mammography. Although the majority of masses are benign lesions such as a cyst or fibroadenoma, a full evaluation is always required to rule out a malignancy. Assessment begins with a detailed history to elicit risk factors for breast cancer. Patients at higher risk are those who have had prolonged exposure to estrogens, as occurs with young age of menarche, late menopause, history of exogenous hormone use, and nulliparity or late pregnancy with first child. A detailed family history is also important in order to determine whether there may be a genetic predisposition to the development of breast cancer. Physical examination includes inspection and palpation of both breasts and the axillae, followed by imaging.

Guidelines for early detection of breast cancer vary, but generally include a baseline mammogram at 40 or 50 years of age, followed by mammography every 1–2 years. Suspicious findings may include an area of microcalcifications (Fig. 21.1) or a solid, spiculated mass (Fig. 21.2). The BI–RADS classification system uses a scale of 0–5 to rate mammographic findings, with 0 meaning an insufficient exam, 1 describing a normal exam with no findings, 2 representing benign findings, 3 meaning findings that are probably benign, 4 expressing a suspicious abnormality, and 5 being highly suggestive of malignancy. However, it is important to remember that greater than 10 % of malignant lesions are mammographically occult. Other imaging modalities are also used to assess for breast cancer. Ultrasonography is a useful adjunct in younger patients and for those with breast cysts. Breast MRI can be used in select patients, but is overly sensitive and too nonspecific for use as a general screening test.

Patients with concerning findings should undergo biopsy of the site to determine the pathology. If the lesion is easily palpable, a fine needle aspiration or core biopsy can be performed. For non-palpable masses, imaging-guided biopsies such as a stereotactic biopsy can be obtained.

If the biopsy results demonstrate invasive breast cancer, the next step for most patients is formal surgical resection of the tumor. An extensive metastatic work-up is not required in the absence of specific symptoms. Patients with invasive breast cancer have essentially two options for surgical therapy: a modified radical mastectomy, or lumpectomy with adjuvant breast radiation. Large, multicenter studies with long-term follow-up have demonstrated that both approaches result in equivalent overall survival, and therefore treatment decisions should be made on a patient-by-patient basis. Preoperative chemotherapy is occasionally used for patients with inflammatory breast cancer, or for those with large tumors in whom a reduction in tumor size would allow breast-conserving therapy.

Axillary lymph node staging is an important factor in determining treatment and prognosis in patients with invasive breast cancer. Patients with enlarged palpable nodes in the axilla likely have nodal involvement and should undergo a complete axillary lymphadenectomy in conjunction with breast resection. Patients with a clinically negative axilla can undergo a sentinel lymph node biopsy, which is associated with a significantly lower risk of lymphedema. In the past, if the sentinel node was positive for tumor, patients uniformly underwent completion lymphadenectomy. However, recent findings demonstrate that this procedure may not be necessary in patients with minimal nodal involvement.

Following surgery, decisions regarding adjuvant endocrine therapy and/or systemic chemotherapy are based on the size of the lesion, nodal involvement, the tumor’s hormone receptor status, and the patient’s age and overall health. In general, most patients except those with the smallest node-negative tumors will be recommended to receive systemic chemotherapy. However, the decision to pursue chemotherapy must always be weighed against the associated toxicities, particularly in older patients with multiple comorbidities.

Most breast cancers retain functional estrogen and progesterone (ER/PR), and this feature can be exploited with hormonal treatments that block these sites. Tamoxifen is an agent that acts as an antiestrogen in the breast through competitive binding of the receptor, and is used in premenopausal women. Anastrazole is an aromatase inhibitor that blocks aromatase, the enzyme required for final step of estrogen synthesis, and is used in postmenopausal women. The use of antihormonal agents has been shown to decrease recurrence and improve outcomes in patients with ER/PR positive breast cancer.

Targeted therapy for breast cancer represents a recent significant advance in the field. HER2 is a transmembrane receptor whose downstream signaling is involved in cell proliferation. Amplification of the source gene for HER2 occurs in a subset of breast cancers, and is strongly associated with a worse prognosis. Trastuzumab is a monoclonal antibody that binds with the receptor and interferes with its function. In patients with HER2-positive breast cancer, trastuzumab therapy has been shown to result in longer survival.

Other than invasive breast cancer, another potential biopsy finding is ductal carcinoma in situ (DCIS). This lesion typically manifests on a mammogram as an area of microcalcifications, usually with no corresponding palpable mass. DCIS is considered a precursor to invasive breast cancer, but lacks metastatic potential because the malignant cells have not yet penetrated the basement membrane. Complete excision of the area with a lumpectomy and adjuvant radiation is sufficient treatment, although patients with DCIS involving a large portion of the breast may require a mastectomy to clear all the disease. In pure DCIS, the chance of lymph node metastases is negligible, and therefore lymph node sampling is not generally indicated. However, if the entire breast is diffusely involved with DCIS, a small focus of invasive cancer may escape detection, and sentinel lymph node biopsy can be considered. Tamoxifen may be recommended in select patients with DCIS who are considered to be high risk.