Axillary lymph nodes: drainage of the upper limb and breast
The axillary lymph nodes in the armpit receive most of the lymph, which the nodes filter, from the upper limb and from the breast.
Remember
The axillary lymph nodes in the armpit drain the upper limb and most of the breast, so infection in the arm and breast cancer commonly involve them. Breast cancer usually spreads to the axillary lymph nodes first.
Lymph from a region of the body drains first to a particular group of nodes, which filter it and look for germs. For the upper limb, that group is the axillary lymph nodes in the armpit (the axilla). Lymph from the hand and forearm travels in superficial vessels that run alongside the superficial veins. Some of it passes through small cubital (elbow) nodes on the way, but the axillary nodes receive most of it.
Most of the lymph from the breast drains to the axillary nodes. In one anatomy text, about 75% of breast lymph goes to the axillary nodes. Smaller shares go to the parasternal nodes beside the breastbone (about 20%) and the posterior intercostal nodes along the back of the chest (about 5%).
Cancer cells that spread through lymphatic vessels travel in the same direction as lymph, so the first nodes draining a tumour are the first it is likely to reach. A tumour in the upper outer quadrant (the upper outer part) of the breast lies closest to the armpit, so breast cancer there usually spreads first to the axillary nodes. The surgeon may sample the sentinel node (the first node in the drainage pathway) to check for spread.
An infected cut on the hand or forearm can make the armpit nodes tender and swollen, because the nodes respond by making more immune cells. This is reactive lymphadenopathy (lymphadenopathy means enlarged lymph nodes). Taking out axillary nodes during breast cancer treatment can impair lymphatic drainage from the arm, and lymphoedema, a long-term swelling of the arm, may follow later.
Key facts
- Upper limb
- most of the lymph from the hand, forearm and arm finishes in the axillary nodes in the armpit.
- Breast
- in one anatomy text, about 75% of breast lymph reaches the axillary nodes, about 20% the parasternal nodes and about 5% the posterior intercostal nodes.
- Other regions
- the cervical nodes in the neck drain the head and neck, and the inguinal nodes in the groin drain the lower limb.
- Arm infection
- an infection in the hand or forearm can cause tender, enlarged axillary nodes.
- Sentinel node
- the first node in the drainage pathway may be sampled during surgery to check whether cancer has spread.
- After node removal
- taking out axillary nodes can impair drainage from the arm, and lymphoedema, a long-term swelling of the arm, may follow later.
Exam traps
- Cubital (elbow) nodes are an intermediate station, but for only part of the limb, so they do not receive most of the lymph from the upper limb: the axillary nodes do.
- Parasternal nodes beside the breastbone take about 20% of breast lymph and form the main alternative route, yet a tumour in the upper outer quadrant of the breast does not usually reach them first.
- Supraclavicular nodes above the collarbone lie downstream of the axillary group, so lymph from the forearm reaches the axillary nodes before them.
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