Chapter 21: Breast

Learning Objectives

Introduction

This chapter focuses on laboratory testing relevant to breast cancer. Infections of the breast are included in Chapter 5.

Breast Cancer

Description

Cancers of the breast constitute a major cause of mortality in women of Western countries. In the United States, the lifetime probability that a woman will develop breast cancer is 1 in 8. Breast cancer accounts for 29% of new cancer cases and 14% of cancer deaths in American women. About 1% of breast cancers occur in males. The risk of developing breast cancer is influenced by several factors. These factors include increased age, family history of breast cancer (especially in a first-degree relative), hormonal factors (early age at menarche, older age of menopause, older age at first full-term pregnancy, fewer number of pregnancies, and use of hormone replacement therapy), clinical factors (high breast tissue density and benign breast diseases associated with atypical hyperplasia), obesity, and alcohol consumption. Since 1990, the mortality rate associated with female breast cancer has decreased in the United States, a decline that has been attributed to both therapeutic advances and early detection.

For localized breast cancer, primary treatment typically consists of either breast-conserving surgery and radiation or mastectomy. Most patients with invasive breast cancer subsequently receive systemic adjuvant chemotherapy and/or hormone therapy, both of which have been shown to reduce systemic recurrence and breast cancer-related mortality. However, the fact that some patients who lack lymph node involvement are cured by the combination of surgery and radiotherapy suggests that adjuvant treatment may not be necessary in all cases. Therefore, to rationally administer adjuvant therapy to patients with local disease, several prognostic factors are considered to assess the risk for recurrence. These prognostic factors include tumor size, axillary node involvement, histological type, cytological grade, lymphatic and vascular invasion, and certain biomarkers associated with breast cancer.

While adjuvant therapy improves patient outcomes, 25% to 30% of women with lymph node-negative and at least 50% to 60% of women with node-positive disease develop recurrent or metastatic disease. Metastatic breast cancer is currently regarded as incurable. Therapeutic options for metastatic disease include chemotherapy, hormone therapy, and molecularly targeted therapies. In the context of metastatic disease, information gained from serial monitoring of tumor markers detected in the serum may contribute to decisions to continue or terminate a particular treatment.

Laboratory Testing

Tissue-based Biomarkers in Breast Cancer

Assessment of biomarkers in tissue obtained from the patient's breast tumor is routinely performed to obtain prognostic information and to guide therapy.

Estrogen Receptor (ER) and Progesterone Receptor (PR)

ER and PR are intracellular receptors that ...