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Supratrochlear lymph nodes

The supratrochlear lymph nodes, also known as epitrochlear or cubital lymph nodes, are a small group of one to four superficial lymph nodes located on the medial aspect of the , approximately 4–5 cm proximal to the (epitrochlea), within the subcutaneous medial to the . They serve as an intermediate station in the superficial of the , filtering lymph fluid primarily from the ulnar (medial) side of the hand—including the third, fourth, and fifth fingers—and the medial , before efferent vessels direct it toward the . Anatomically, these nodes exhibit interindividual variations in number and precise patterns, with one or two nodes being most common and up to three or four occurring rarely; they are typically nonpalpable in healthy individuals due to their small size and subcutaneous position near the bifurcation. Their functional involves immune surveillance, where resident lymphocytes and macrophages process antigens from incoming to mount responses against pathogens or abnormal cells, contributing to the overall lymphatic clearance of the upper extremity. Clinically, supratrochlear lymph nodes become palpable and enlarged (often >1 cm) in response to infections, inflammatory conditions, or malignancies affecting the or systemically, such as , (where they appear discrete and "shotty"), (matted with possible caseation), lymphomas, or metastases from . Palpation of these nodes aids in the of elbow swelling, as they remain uninvolved in traumatic effusions but enlarge in infectious or arthritic processes. In oncology, their involvement can signal interval nodal spread, particularly in upper limb cancers, and sonography reveals characteristic features like hypoechoic enlargement with hilar vascularity in reactive states versus peripheral flow in metastases.

Anatomy

Location and relations

The supratrochlear lymph nodes, also referred to as epitrochlear nodes, consist of one to two small lymph nodes situated superior to the in the subcutaneous on the medial aspect of the , approximately 4–5 cm above the humeral epitrochlea. These nodes are positioned medial to the within the and in close proximity to the bifurcation of the . Classified as a of the cubital (or epitrochlear) lymph nodes, they form part of the superficial lymphatic structures of the . In relation to surrounding structures, the supratrochlear nodes overlie the , lie adjacent to the and , and are in proximity to the flexor muscles of the that bound the medially.

Structure and histology

The supratrochlear lymph nodes, also known as epitrochlear nodes, are small, oval-shaped structures typically measuring less than 0.5 in diameter in their non-enlarged state. These nodes are encapsulated by a thin layer of composed of collagenous fibers and stroma, which provides structural support and delineates the node from surrounding . Afferent lymphatic vessels enter the node through the convex surface, delivering for , while efferent vessels exit via the hilum, a depressed on the concave side where blood vessels also penetrate. Histologically, the supratrochlear lymph nodes exhibit the standard architecture of secondary lymphoid organs, divided into an outer , inner paracortex, and medulla. The cortex features B-cell follicles, which may be primary (dense aggregates of resting B lymphocytes) or secondary (with pale-staining germinal centers surrounded by a of B cells, containing proliferating B cells, , and tingible body macrophages). Adjacent to the cortex lies the paracortex, enriched with T lymphocytes and interdigitating dendritic cells, supported by a network of reticular fibers that form a supportive throughout the node; this region also contains high endothelial venules specialized for the entry of circulating lymphocytes from the bloodstream. The medulla consists of medullary cords and , where cords comprise plasma cells, macrophages, and lymphocytes, facilitating antibody production and . Medullary , lined by endothelial cells and filled with , connect to cortical sinuses and the subcapsular sinus, enabling the flow and filtration of through the via macrophages and reticular fibers that trap particulates and pathogens. This layered organization supports the 's role in immune surveillance, with trabeculae from the capsule extending inward to compartmentalize these regions.

Function

Lymphatic drainage

The supratrochlear lymph nodes primarily receive from the ulnar aspect of the hand, encompassing the , , and little fingers (digits 3 through 5), as well as the skin and subcutaneous tissues of the medial . These nodes, positioned superior to the along the , serve as key collectors for superficial lymphatics in this region. Afferent lymphatic vessels originate from the superficial network in the medial hand and forearm, where capillaries in the skin and subcutaneous tissues converge and travel alongside the toward the supratrochlear nodes. This pathway ensures efficient collection of interstitial fluid and cellular debris from the ulnar-side structures before filtration in the nodes. Efferent vessels from the supratrochlear nodes direct to the deeper brachial lymph nodes along the and veins, subsequently progressing to the lateral (humeral) group of for further processing. Within the broader lymphatic , the supratrochlear nodes act as intermediate stations, bridging superficial drainage from the distal ulnar regions to the central axillary nodes, which ultimately connect to the subclavian lymphatic trunks and venous circulation. This arrangement facilitates unidirectional flow from peripheral tissues toward the , integrating with deep and superficial pathways throughout the arm.

Immune role

The supratrochlear lymph nodes, located at the medial elbow, serve as key filters for lymph originating from the medial hand, forearm, and ulnar regions of the upper limb. Macrophages residing in the subcapsular and medullary sinuses capture and trap pathogens, antigens, and cellular debris from this lymph, initiating the innate immune response by phagocytosing harmful agents and preventing their further spread through the lymphatic system. Within these nodes, the trapped antigens are presented to lymphocytes, driving adaptive immunity through interactions in the cortical and paracortical regions. In the , B cells encounter antigens via , leading to their proliferation, differentiation into plasma cells, and production of antibodies targeted at infections or foreign substances from the . Concurrently, in the paracortex, T cells are activated by dendritic cells displaying processed antigens, resulting in the expansion of cytotoxic and helper T cell populations that coordinate targeted immune responses. As nodes for the , the supratrochlear lymph nodes provide first-line immune surveillance, rapidly detecting and responding to localized threats such as bacterial or viral invasions in the drained tissues, thereby facilitating efficient antibody-mediated and cell-mediated cytotoxic effects. Activated lymphocytes and secreted cytokines from these processes exit via efferent lymphatic vessels, draining toward the to amplify and integrate the response into broader systemic immunity.

Clinical significance

Pathological conditions

Supratrochlear lymph nodes can become enlarged due to infectious processes originating in the hand or forearm, reflecting their role in regional lymphatic drainage. In bacterial infections such as those caused by Staphylococcus aureus or streptococci, the nodes typically present as tender, erythematous swellings that may suppurate, often accompanying primary pyoderma or infected skin lesions in the distal upper extremity. Cat-scratch disease, caused by Bartonella henselae, commonly involves these nodes, presenting as tender, enlarged lymphadenopathy following a cat scratch on the hand or forearm. Tuberculosis infection of the elbow or adjacent structures leads to characteristic matted, caseating enlargement of these nodes, potentially progressing to form cold abscesses without significant overlying inflammation. Such tuberculous lymphadenopathy is observed in approximately 20-30% of elbow tuberculosis cases, aiding in clinical differentiation from other etiologies. Inflammatory conditions like involving the joint result in discrete, shotty enlargement of the supratrochlear nodes, which appear as small, firm, mobile nodules palpable above the medial epicondyle. This correlates with active and joint destruction, as documented in radiographic studies of affected elbows, though it is not a universal finding in all rheumatoid cases. Malignant involvement of supratrochlear lymph nodes occurs via metastatic spread from skin cancers, particularly of the hand or , where these nodes serve as an interval site before axillary drainage. Affected nodes are typically firm, fixed, and non-tender, indicating tumor infiltration, with epitrochlear (synonymous with supratrochlear) involvement reported in up to 10-15% of distal upper extremity s undergoing . Similarly, or other hand tumors can metastasize to these nodes, prompting evaluation for regional nodal basins in staging. In contrast, supratrochlear lymph nodes remain non-enlarged in acute traumatic injuries to the , such as fractures or contusions, which helps distinguish trauma from infectious or inflammatory causes during .

Diagnostic and therapeutic applications

of the supratrochlear lymph nodes serves as an initial diagnostic tool in evaluating a swollen , aiding in the of underlying conditions. These nodes are typically not enlarged in cases of traumatic elbow joint injury, whereas enlargement is observed in inflammatory or infectious etiologies such as , where nodes appear discrete and shotty, or , where they may be matted and associated with caseation. Imaging modalities like and computed tomography () are employed to assess supratrochlear node characteristics, including size, matting, and the presence of abscesses. provides detailed evaluation of node shape, cortical thickness, hilum, and vascularity via color Doppler, facilitating differentiation between reactive, inflammatory, and neoplastic involvement. is useful for confirming abnormalities, particularly in staging scenarios, and may be combined with for detecting metastatic uptake. is performed under guidance to obtain cytology samples in suspected , aiding in the identification of metastatic cells. Surgical , often involving excision, is indicated for histopathological confirmation in cases of suspected or cancer, providing definitive when and are inconclusive. Therapeutically, supratrochlear dissection is relevant in upper , particularly when identifies involvement in this basin, as it contributes to regional and prognostic assessment alongside axillary . For infectious es, such as those in , management includes antibiotic therapy—often anti-tubercular drugs—and surgical drainage if the abscess does not resolve medically.

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