Introduction

The lymphatic system consists of a collection of lymphatic vessels connected to lymph nodes which filter lymph fluid that gets collected throughout the body. Lymph nodes filter lymph via specialized white blood cells that destroy and remove microorganisms, malignant cells, damaged cells, and foreign particles.  The lymphatic vessels and lymph nodes, along with the thymus, tonsils, and spleen, serve a vital function for the removal of interstitial fluid from tissue and development and maintenance of the immune response. Lymph fluid ultimately returns to the venous circulation. 

Lymph nodes are present throughout the body.  The head and neck region contains over 300 lymph nodes, of which include the supraclavicular lymph nodes.[1] This paper will focus on the supraclavicular lymph nodes and their anatomical relations, drainage, physiological variations, surgical considerations, and clinical significance in the context of malignancy and other pathology.

Structure and Function

Classification

There have been several ways to classify cervical lymph nodes, which can become quickly confusing for students.[2] Based on a Roman numeral “level” system classification (from IA, IB, II, III, IV, V, VI) by the American Joint Committee on Cancer (AJCC), the supraclavicular lymph nodes belong to sublevel Vb: the posterior triangle group. This level is bounded:

• Superiorly by the horizontal line defined by the lower border of the cricoid cartilage
• Inferiorly by the clavicle
• Medially (anteriorly) by the sternocleidomastoid (SCM) muscle or sensory branches of cervical plexus
• Posteriorly (laterally) by the anterior border of the trapezius muscle

The Virchow node (VN), named in honor of the German pathologist Rudolf Virchow, is an end node or the most proximal of left supraclavicular lymph nodes. Unlike the rest of the left supraclavicular lymph nodes, it belongs to the IV level which is near the jugulo-subclavian venous confluence and, usually, lying on the scalenus anterior muscle and posterior to the platysma and the sternocleidomastoid muscles.[3][4] If classified by region, the supraclavicular lymph nodes would qualify as inferior deep cervical nodes.

Anatomical boundaries

The supraclavicular lymph node chains have an investing fat pad, which is bounded by the following structures[5]:

• Posteriorly: by the scalene muscles; hence, which leads to their reference as scalene nodes in some texts
• Anteriorly: by the sternocleidomastoid muscle
• Medially: by the common carotid artery and internal jugular vein
• Laterally by lateral edge of the sternocleidomastoid

Drainage

Generally speaking, both right and left supraclavicular lymph nodes drain the neck via efferent lymphatic vessels coming from the accessory nerve lymph node chains, which belong to sublevel Va.[1] However, these nodes mainly drain structures in the thorax and abdomen. More specifically, the right supraclavicular lymph nodes drain the breast, lung and upper esophagus, while the left supraclavicular lymph nodes have more extensive drainage sites and drain distant regions which include but are not limited to the kidney, cervix, testis, and pancreas through various and complicated lymphatic pathways which are out of the scope of this text. The right supraclavicular lymph nodes then drain into the right lymphatic duct, while the left supraclavicular lymph nodes drain into the thoracic duct.[6]

Blood Supply and Lymphatics

The skin flap in which the supraclavicular nodes lie within is mainly supplied by the supraclavicular vessels, which usually branch from the transverse cervical artery. When harvesting the lymph nodes without the skin paddle, they primarily receive blood supply the transverse cervical vessels. The transverse cervical artery originates from the thyrocervical trunk of the subclavian artery. After that, it courses transversely under the inferior belly of the omohyoid muscle and anterior to scalene muscle and the phrenic nerve as it reaches the levator scapulae muscle to give its branches. The transverse cervical artery offers various branches that pass through the supraclavicular nodes and supply them.[7]

Nerves

The significant nerves which are related to the supraclavicular lymph nodes are the phrenic and the vagus nerves which lie lateral and medial to the internal jugular vein, respectively.[7]

The phrenic nerve arises from the ventral rami of roots (C3-C4-C5) and receives a contribution from the cervical sympathetic ganglia. The nerve forms at the superior lateral border of the anterior scalene muscle and then descends obliquely towards the medial side of the anterior scalene muscle (staying deep to the prevertebral fascia, the supraclavicular lymph nodes and the transverse cervical vessels). As the nerve approaches the root of the neck, it usually traverses between the subclavian artery and vein and descends to the mediastinum to supply the diaphragm muscle.[8]

The vagus nerve takes its origin in the medulla oblongata from various nuclei which are out of the scope of the text. The vagus nerve then exits the skull via the jugular foramen and descends inside the carotid sheath posterior and lateral to the common and internal carotid arteries and medial to the internal jugular vein. The right and left vagal nerves then descend anterior to the subclavian arteries to the thorax and the abdomen.[9] 

Physiologic Variants

The exact number of the supraclavicular lymph nodes, including the Virchow node, and their distance from anatomical boundaries surrounding it can vary to an extent.

In a study done to provide a detailed description of the surgical anatomy of the supraclavicular lymph node flap for free vascularized lymph node transfer, a surgical method to treat lymphedema, dissections on fresh cadavers showed variation in the number of lymph nodes between the right (average of 1.5 +/- 1.85) and left supraclavicular lymph nodes (average of 3 +/- 2.26). In four out of nine cases, no right supraclavicular lymph nodes were present on the right side while in one out of nine cases, no left supraclavicular lymph nodes were present. Researchers also noted a variation in their mean distance from the jugular notch in the right (8.29 +/- 2.15) and left sides (6.10 +/- 1.21).[10]

Studies have also noted variations in the location of the Virchow node and its histological anatomy relative to the thoracic duct. A study done on five cadavers found that the Virchow node was attached to the dorsal aspect of the carotid sheath (two out of five cadavers) or on the scalenus anterior muscle (three out of five). The study noted different numbers of collaterals coming from the thoracic duct and their communication pattern with the Virchow node. It is also noteworthy that the Virchow node is not always present at the terminal of the thoracic duct (only present in 27% of Japanese subjects).[3]

Surgical Considerations

Investigations of supraclavicular lymph nodes masses include imaging techniques such as computed tomography (CT) or positron emission tomography (PET) followed by ultrasound-guided fine needle aspiration cytology (FNAC).[11][12] Although rapid, painless, inexpensive, safe and does not require anesthetic or hospital admission, FNAC comes with its disadvantages, which include the inability to provide the cellular architecture required for accurate subtyping of lymphomas. Thus, invasive procedures that provide a greater volume of tissue such as an open biopsy of the supraclavicular lymph nodes are an option when the FNAC is nondiagnostic. Despite excisional biopsy being the gold standard in lymphoma cases, a core needle biopsy should be performed alternatively, as it provides adequate results and is less invasive.[13] According to the latest guidelines set by the American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS), an open biopsy is only necessary if FNAC, core needle biopsy, physical examinations, and other ancillary test prove to be undiagnostic.[14]

As with any surgical procedure, procedures involving the supraclavicular lymph node require a firm grasp of the critical structures and anatomy that surround it. Complications that could arise from procedures such as supraclavicular lymph node harvest or biopsies include but are not limited to[15][14]:

• Carotid and subclavian artery bleeding
• Chylous fistulas, the leaking of lymph from lymphatic vessels, caused by damage to lymphatics such as the thoracic duct
  • Chylous fistulas are preventable by asking the patient to cough; this will compress the intrathoracic lymphatics leading to distension of lymphatic vessels outside the thorax, resulting in a jet of chyle leaking from places of the defect, allowing their localization and ligation before closing the wound.
• Damage to the phrenic nerve, which could lead to dyspnea as the phrenic nerve supplies the diaphragm
• Wound infection
• Tumor seeding in cases of human papillomavirus-positive head and neck squamous cell carcinoma (HPV-positive HNSCC)

Clinical Significance

Generally speaking, most neck masses in children are of infectious etiology. In adults, however, neck masses in patients who are greater than or equal to 18 years old should always be considered to be malignant until proven otherwise. Thus, the clinical approach to neck masses for adults vs. children vary greatly. It is crucial to keep in mind that cancers of the head and neck, such as squamous cell carcinoma (HNSCC), lymphoma, thyroid, or salivary gland, can present initially as asymptomatic masses.[16][14] Because of this, young adults presenting with an asymptomatic neck mass and an insignificant history may have their diagnosis for underlying malignancies such as mucosal HPV-positive HNSCC delayed.

The differential diagnosis for lymphadenopathy is extensive. It generally categorizes as neoplastic, infectious, inflammatory, reactive, and nondiagnostic. Researchers performed a retrospective 5-year study in a large hospital on 309 supraclavicular masses diagnosed with fine needle aspiration. Results showed that the majority of masses (55%) were malignant, with secondary (metastatic spread) being far more frequent than primary lymphomas (47% vs. 8%, respectively). The most common metastatic malignancies were of lung, breast, uterine, and esophageal origin.[17]

Enlargement of VN, a significant clinical finding termed Troisier sign, can indicate advanced stage 4 gastrointestinal metastasis, which is associated with a 5-year survival of 4%.[6] Other etiologies include, but are not limited to, lymphoma, breast, esophageal, pelvic and testicular cancers.[18] Because of its anatomical relations to critical structures such as the phrenic nerve, the subclavian vessels, and the brachial plexus, enlargement of this node can compress these structures and cause various pathologies such as unilateral phrenic neuropathy, which might lead to dyspnea, vascular and neurogenic thoracic outlet syndromes, and Horner syndrome. Horner syndrome is due to the compression of the lower part of the brachial plexus (C8-T1), leading to the disruption of sympathetic innervation of the eye and usually manifests as four key clinical signs on the ipsilateral side: miosis (constricted pupil), ptosis (droopy eyelid), anhydrosis (decreased sweating) and enophthalmos (sunken eyes). Thus, the presence of a Troisier sign should be kept in consideration when any of these pathologies are present.[19][20]