Internal Thoracic Artery Branches (Breast)

The internal thoracic artery (formerly called the internal mammary artery) contributes significantly to the arterial supply of the medial portion of the breast through its perforating branches. These branches arise from the proximal part of the artery as it descends along the inner thoracic wall, and they pierce the intercostal spaces to supply the breast parenchyma, overlying skin, and subcutaneous tissues. This vascular supply is particularly important in lactation, reconstructive surgery, and breast imaging.

Origin of the Internal Thoracic Artery

The internal thoracic artery arises from the first part of the subclavian artery in the root of the neck. It descends vertically along the posterior surface of the anterior thoracic wall, approximately 1–2 cm lateral to the sternum, and terminates at the sixth intercostal space by dividing into the superior epigastric and musculophrenic arteries.

Relevant Branches Supplying the Breast

As it courses downward, the internal thoracic artery gives off paired branches in each upper intercostal space. The branches particularly relevant to the breast are:

Anterior intercostal arteries (1st–6th spaces): These supply the intercostal muscles and contribute small collateral vessels to the lateral breast via anastomoses.
Perforating branches (2nd–4th intercostal spaces): These are the most significant for breast perfusion. They pierce the intercostal muscles and overlying pectoral fascia to enter the parenchyma of the medial breast.

The second and third perforating branches are typically the largest and most important contributors to breast vascularity. They penetrate deeply into the glandular tissue and are often involved in reconstructive and oncologic planning.

Anastomoses and Vascular Territories

The internal thoracic artery branches form extensive anastomoses with other arteries that supply the breast, including:

Lateral thoracic artery (from the axillary artery)
Posterior intercostal arteries (from the thoracic aorta)
Thoracoacromial artery branches (pectoral branch)

These anastomotic connections ensure a robust collateral network, which is vital during pregnancy, lactation, or surgical flap creation. The medial half of the breast is predominantly supplied by the internal thoracic artery, while the lateral half receives most of its blood from the lateral thoracic and axillary branches.

Functional and Surgical Significance

Lactation: Blood flow through these branches increases significantly during pregnancy and lactation to support the metabolic demands of milk production.
Reconstructive surgery: The internal thoracic perforators are used in perforator flaps (e.g., IMAP flaps) and are a reference point for DIEP and TRAM flap planning.
Coronary artery bypass grafting (CABG): The internal thoracic artery (usually the left) is a preferred vessel for grafting, and its use must be considered in patients with prior or future breast surgeries.

Imaging and Clinical Relevance

On Doppler ultrasound, the perforating branches of the internal thoracic artery can be visualized in the parasternal region, particularly in lactating women or those with increased breast vascularity. In contrast-enhanced breast MRI, these branches contribute to the enhancement pattern of the medial breast. Obstruction or disruption of these vessels (e.g., during surgery or trauma) can lead to ischemic complications or delayed wound healing.

In oncological contexts, tumors located medially in the breast may derive part of their blood supply from these vessels, and knowledge of their course is crucial during mastectomy or tumor excision to minimize bleeding and preserve tissue viability.