Learning Objective

By the end of this lesson, the learner should be able to describe the surface anatomy, internal structure, vascular supply, lymphatic drainage, nerve supply, and major clinical correlations of the female breast, especially the anatomical basis for the spread and presentation of breast cancer.

Overview

The breasts are paired structures located on the anterior thoracic wall in the pectoral region. They are present in both males and females, but become significantly more prominent in females after puberty due to hormonal influence. The mammary glands are accessory glands of the female reproductive system responsible for lactation.

This lesson focuses on the anatomy of the female breast, including structure, vascular supply, lymphatic drainage, innervation, and clinical relevance.

Surface Anatomy

The breast extends from the 2nd to the 6th costal cartilages and from the lateral border of the sternum to the mid-axillary line. It lies superficial to the pectoralis major and serratus anterior muscles.

The breast has two regions:

Circular body – the largest and most prominent part
Axillary tail (of Spence) – extends into the axilla

Clinical importance: The axillary tail is a common site of breast carcinoma spread. The nipple consists mainly of smooth muscle fibers and is surrounded by the pigmented areola.

The areola contains sebaceous (Montgomery) glands that enlarge during pregnancy and lubricate the nipple.

Activity

Anatomical Structure

The breast is composed of mammary glands embedded in connective tissue stroma.

Mammary Glands

There are 15–20 lobes, each draining via a lactiferous duct into the nipple. Each lobe contains lobules, and each lobule contains alveoli that produce milk. The lactiferous ducts converge at the nipple like spokes of a wheel.

Connective Tissue Stroma

The stroma has fibrous and fatty components. Suspensory ligaments (Cooper’s ligaments) anchor the breast to the dermis and pectoral fascia.

Clinical importance: Shortening of Cooper’s ligaments due to tumor invasion causes skin dimpling.

Activity

Pectoral Fascia and Retromammary Space

The base of the breast rests on the pectoral fascia covering the pectoralis major. The retromammary space is a potential space between the breast and pectoral fascia.

Non-clinical correlation: This space allows breast mobility over the chest wall.

Clinical importance: The retromammary space is used in reconstructive breast surgery.

Vasculature

Arterial Supply

Medial supply is from the internal thoracic (internal mammary) artery. Lateral supply is from branches of the axillary artery (lateral thoracic and thoracoacromial). Lateral mammary branches arise from posterior intercostal arteries (2nd–4th spaces).

Venous Drainage

Venous drainage parallels arterial supply and drains into the axillary and internal thoracic veins.

Lymphatic Drainage

75% of lymph drains to the axillary lymph nodes.

Additional drainage:

Parasternal nodes – 20%
Posterior intercostal nodes – 5%

The nipple and areola drain into the subareolar lymphatic plexus (of Sappey).

Clinical importance: Lymphatic drainage explains the early spread of breast cancer to axillary nodes.

Nerve Supply

Innervation is via anterior and lateral cutaneous branches of T4–T6 intercostal nerves. These nerves provide sensory and autonomic fibers.

Milk production is NOT neurally controlled. Prolactin stimulates milk production; oxytocin stimulates milk ejection. Both hormones are secreted by the pituitary gland.

Clinical Relevance

Breast Cancer

Breast cancer is one of the most common malignancies in women worldwide. The peau d’orange appearance results from lymphatic obstruction, causing skin edema. Nipple retraction occurs due to fibrosis and shortening of Cooper’s ligaments.

Axillary lymph nodes are most commonly involved in metastasis. Distant spread may involve the liver, lungs, bones, and ovaries.