Anatomy clinical correlates: Breast

The breasts, formally known as the mammary glands, are situated in the subcutaneous tissue overlying our pectoralis muscles. There are many conditions that can affect the breast, the most well known being breast cancer. Breast cancer, as well as other conditions that can affect the breast, can often go unnoticed, which has serious clinical consequences; so It is important to understand and recognize these conditions as early as possible.

So let’s start with breast cancer, which causes changes to the structure and appearance of the breasts. One of the classic changes is the presentation of a palpable breast mass, which is typically a hard, immobile lesion with irregular borders most commonly found in the upper outer quadrants.

Another indication of more advanced disease are skin changes, specifically the orange-peel appearance, also called the peau d’orange sign, which happens when there’s prominent edema and dimpling of the overlying skin. Larger dimpling of the skin can result from cancerous invasion of the glandular tissue and fibrosis, which may also pull on the suspensory ligaments of the breast and can cause retraction of the nipple.

If the cancer interferes with the lymphatic drainage this can lead to lymphedema, which is when there’s excess fluid in the subcutaneous tissue. This in turn results in deviation of the nipple and the skin appears thickened and leather-like. Cancer cells can spread through contiguity, which is when the adjacent tissue is invaded.

When breast cancer cells invade the retromammary space or the pectoral fascia, or when they metastasize to the interpectoral nodes, the breast elevates when the muscle contracts, and this usually signals advanced cancer. Furthermore, the local cancerous invasion to the pectoral fascia and pectoralis major muscle below may result in deep fixation of the breast tissue.

Breast cancer usually spreads through lymphatic vessels, which basically carry cancer cells from the breast to the lymph nodes, especially those in the axilla. Communications among lymphatic pathways and among axillary, cervical and parasternal nodes can cause metastases from the breast to develop in the supraclavicular lymph nodes, in the opposite breast or in the abdomen, but the most common site of metastasis of breast cancer remains the axillary lymph nodes.

Cancer cells can also spread from the breast through venous routes. For example, the posterior intercostal veins drain into the azygos system of veins alongside the bodies of the vertebrae. As a consequence, cancer cells can spread to the vertebrae and from there to the cranium and brain.

Breast cancer mainly affects biological females, and it is the most commonly diagnosed malignancy in women in the United states. However, up to 1.5% of cases occur in biological males.

In males, the cancer also usually metastasizes to the axillary lymph nodes in addition to bone, pleura, lung, liver and skin. In male individuals, a visible or palpable subareolar mass or secretion from a nipple can suggest breast cancer.