Lymph nodes are small, bean-shaped glands that are an integral part of the body’s immune system. They act as filters, monitoring and cleansing lymph fluid as it circulates throughout the body. Within lymph nodes, immune cells identify and destroy foreign substances, such as bacteria and viruses, and abnormal cells. The epitrochlear lymph node is a specific node with distinct location and role. This article clarifies its anatomical placement within the arm and discusses its importance in health and disease.
Anatomical Placement
The epitrochlear lymph node, also known as the cubital or supraepitrochlear lymph node, is located on the medial side of the arm. It is typically found in the subcutaneous connective tissue, a layer just beneath the skin, positioned near the elbow. This node is situated approximately 2 to 5 centimeters (about 1 to 2 inches) above the medial epicondyle of the humerus.
The medial epicondyle is a prominent bony projection on the inner aspect of the humerus, the long bone of the upper arm, and can be easily felt as a bump on the inside of the elbow. The epitrochlear lymph node lies in this region, sometimes slightly posterior to the basilic vein. Most individuals have one to three epitrochlear nodes, though rarely there can be four.
These nodes are typically small, measuring about 3 to 10 millimeters (approximately 0.1 to 0.4 inches) in a healthy state. Due to their small size, they can often be challenging to feel during a physical examination unless they become enlarged. Their superficial location, however, makes them accessible for palpation when swollen, providing valuable diagnostic clues.
Role in Health and Disease
The epitrochlear lymph node functions as part of the superficial lymphatic system of the upper limb, filtering lymph fluid. This node primarily drains lymph from the hand, forearm, and sometimes the medial aspect of the arm, including the last two or three fingers. Lymphatic drainage patterns can vary among individuals, but the general area served by this node remains consistent.
When the epitrochlear lymph node becomes enlarged or palpable, a condition known as lymphadenopathy, it often signals an underlying pathological process in the regions it drains. This enlargement can indicate infection, inflammation, or, less commonly, malignancy. Infections originating in the hand, forearm, or fingers are common causes of epitrochlear lymphadenopathy.
Specific conditions are frequently associated with an enlarged epitrochlear node. Cat scratch disease, caused by the bacterium Bartonella henselae and often transmitted by a cat scratch or bite, is a notable cause, particularly in children and adolescents. Syphilis, a bacterial infection, can also lead to epitrochlear lymph node enlargement, especially in its secondary stage or if a primary lesion is located in the arm. Sarcoidosis, a systemic inflammatory disease, can also manifest with enlarged epitrochlear nodes, often as part of a more generalized lymphadenopathy.
Other less common causes include certain lymphomas and metastatic cancers, though these typically present with harder, more fixed nodes. Its examination is therefore a meaningful component of a physical assessment for conditions affecting the upper limb.