Microsurgical Procedures: Vascularized Lymph Node Transfer from the Supraclavicular Region

Key points

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Harvesting lymph nodes from the axillary or groin region may cause secondary lymphedema of the upper or lower extremity.
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The main advantage of supraclavicular nodes harvest is minimal risk of secondary lymphedema.
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The flap is designed with or without a skin flap in a horizontal orientation above the clavicle.
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A free style free flap based on the transverse cervical artery and vein, and branches of the external jugular vein can be designed.

Introduction

As vascularized lymph node transfers for the treatment of lymphedema are increasing in popularity and success rates, the aim has shifted towards overcoming potential donor site morbidity and optimizing the harvest target. Most reports of vascularized lymph node transfer have been for the treatment of lymphedema of the upper extremity, using superficial groin lymph nodes. However, this harbors the risk of injury to the deeper lymphatics at the donor site, resulting in secondary lower limb lymphedema. For treatment of lower extremity lymphedema, potential donor sites for lymph nodes are less straightforward. Utilized nodes primarily include the axillary and submental regions; both have significant potential drawbacks, with potential lymphedema of the upper extremity from axillary nodal harvest, and the unsightly donor scar in the submental position, with the risk of marginal mandibular nerve injury during harvest of the proximate nodes.

To date, there is a relative paucity of literature regarding donor site morbidity. Viitanen et al. performed lower limb lymphoscintigraphy on 10 lymphedema patients who had undergone lymphatic transfer from the groin. While none of the patients had donor-site lower limb adverse symptomatology, the lymphoscintigraphy of the majority of patients showed a slightly slower lymphatic flow in the donor limb compared with the nonoperated limb. A semiquantitative evaluation of lymphatic drainage using a numerical transport index revealed that two of ten patients had abnormal lymphatic function in their donor lower limb. Vignes et al. further highlight the potential risks of lymph node transfer from inguinal and axillary donor sites. In a study retrospectively examining 26 cases, 38% had significant donor-site morbidity including secondary limb lymphedema, lymphocele and chronic donor site pain. These findings warrant seeking a less morbid donor lymphatic basin.

Recent anatomical elucidations of the well-described supraclavicular flap have brought us to explore this region as source for vascularized lymph nodes. The abundance of lymph nodes in this location, positioned off of the main drainage pathways of the upper extremity, the redundancy of alternative drainage routes from the head and neck, coupled with favorable scar healing in the area, makes the supraclavicular source advantageous and widely applicable.

Concepts

Regional Anatomy

Lymphatic Anatomy

The supraclavicular chain of nodes, known also as the ‘transverse chain’, is located along the transverse cervical artery (TCA) ( Figure 17.1 ). It receives afferent vessels from the anterolateral neck skin, chest wall, mammary gland, and occasionally from the upper extremity and the infraclavicular nodes. Anterior tributaries connecting the superficial anterior cervical nodes are located in the anterior jugular pathway, draining lymph from the skin and muscles of the infrahyoid region, the isthmus of the thyroid gland and the infraglottic part of the larynx. Tributaries arise laterally from the accessory lymphatic chain, and channels from the superficial external jugular nodes.

The majority of the lymphatic pathways from the breast towards the supraclavicular region are indirect. The infraclavicular (apical) nodes, typically terminating in the scalene nodes posterior to the sternocleidomastoid and clavicle, may drain to the supraclavicular nodes. An ‘axillary bypass’ directly into these nodes may be present in 5–17% of cases.

Efferent lymphatics (typically 2–3) form the supraclavicular trunk, which enters the subclavian venous angle either directly, or via the thoracic duct (or the right lymphatic duct).

In the left neck, the last node intercalated within the thoracic duct after its ascendance in the chest, is referred to as Virchow’s node. It is located at or near the jugulo-subclavian venous junction (also referred to as the venous angle). Lymphadenopathy in the region may be a clinical harbinger of the metastatic disease from abdominal source (particularly from the stomach). This is thought to be due to lymph reflux and trapping of malignant cells from the terminal thoracic duct. Due to its location, this node is not included in the dissection, which is performed at a more superficial plane.

From a clinical standpoint, the American Joint Committee on Cancer (AJCC) and the American Academy of Otolaryngology—Head and Neck Surgery define level V lymph nodes as the posterior triangle group. This includes the supraclavicular lymph nodes. In 2002, amendments were made to this classification suggesting a subdivision of level V into level Va and level Vb. By this designation, level Va nodes are located posterior to the sternocleidomastoid (SCM) muscle, above the horizontal plane defined by the inferior border of the cricoid cartilage, including nodes along the spinal accessory nerve. Level Vb nodes are located posterior to the SCM, caudal to the horizontal plane made by the inferior border of the cricoid cartilage. This group includes the lymph nodes situated along the TCA, previously designated by some authors as a separate, ‘supraclavicular’ group, not included level V. These nodes, of the supraclavicular triangle, are the targets of harvest in this flap’s design.

The terminological clarification is important in understanding the role of these nodes in lymphatic metastases and their relative expendability as evidenced by their physiologically inconsequential harvest in cervical lymph node dissections for oncological purposes. The supraclavicular lymph nodes play a role in drainage of structures of the head and neck as exemplified in studies tracking metastases of head and neck tumors such as papillary thyroid cancer. Current understanding suggests a stepwise progression of lymphatic metastases, rendering level Vb nodes a reasonable target from an oncological perspective, as their involvement in head and neck cancers is relatively low. Head and neck lymph drainage is site-specific and occurs in a predictable fashion. In a paper by Mukherji in 2001, the frequency of supraclavicular nodal involvement in an array of head and neck cancers was surveyed, based on the classic reports of Lindberg and Byers. The frequencies reported were as follows: 11% in nasopharyngeal carcinoma, 1% floor of mouth carcinoma, 4% base of tongue carcinoma, supraglottic 3%, and none in oral tongue, tonsillar, and soft palate cancers. For these reasons level Vb node dissection is not commonly performed in cervical lymph node dissection for staging and curative intents, and is reserved for lateral tumors closer to this region. Similar frequencies are reported in papillary carcinomas of the thyroid, where levels II, III, and IV are more commonly involved.

Using melanoma lymphoscintigraphy data to understand the functional anatomy of the lymphatics draining the skin, the supraclavicular basin appears to play a role in skin drainage of the lateral neck and jawline, albeit secondary to nodes of levels II and IV. The supraclavicular cluster does not appear to play a role in drainage of upper extremities (which drain to the various axillary nodes, and subsequently to the subclavian trunk).

Vascular Anatomy

Cordova et al. reported their vascular investigation of the supraclavicular region in 2009. The TCA emanates from the thyrocervical trunk, posterior to the sternocleidomastoid muscle. The vasculature is relatively constant, with the TCA commonly originating from the thyrocervical trunk (80%), directly from the subclavian artery (17%) or as a branch of the internal mammary artery in a small minority of cases. The TCA courses posterolaterally approximately 2 cm above the clavicle towards the trapezius, deep to the inferior belly of the omohyoid. The TCA gives off a superficial and a deep branch. An average of four perforators to the supraclavicular skin arise from the superficial branch of the TCA (majority of cases); to a lesser degree directly from the TCA; and occasionally from the deep, terminal branch of the TCA. Mixed variants may exist. A separate supraclavicular branch of the TCA runs a lateral course superior to the clavicle, supplying the skin flap ( Figure 17.2 ).

Venous tributaries accompanying the TCA perforators coalesce into one or two vena comitantes of the TCA, draining ultimately into the transverse cervical vein (TCV). A separate, superficial venous system appears to be the main venous outflow, draining into the external jugular vein (EJV) via the superficial cervical vein. The deep system (i.e., the venae comitantes of the TCA) serves a secondary role in drainage. This observation is the rationale for incorporating superficial veins (typically the EJV) to serve as the venous drainage for the transferred flap. Venous perforators consistently accompany the arterial ones. Although the superficial cervical vein tributaries consistently drain into the external jugular vein, connections between the vena comitantes and the EJV are not always present.

The length of the pedicle ranges between 3 and 6 cm. The arterial diameter is between 1.5 and 2.5 mm, with the EJV usually greater than 3.0 mm or TCV ranging between 2.0 and 3.0 mm in diameter.

Flap Design

The flap can be harvested with or without a skin flap. When skin flap is included, it is typically designed with an elliptical skin paddle oriented horizontally just above the clavicle ( Figure 17.3 ). The posterior border of the clavicular insertion of sternocleidomastoid muscle is usually the midpoint of the ellipse. The skin and the supraclavicular lymph nodes are harvested en bloc, with the skin paddle serving as a monitor. Preserving the skin and subcutaneous tissue also obviates disruption of lymphatic channels that, in theory, may re-establish connections to recipient site lymphatics. The dimensions of the skin flap that enable tension-free primary closure are approximately 3 × 10 cm. As mentioned above, the EJV runs through the flap and is typically the major outflow, and thus should be selected for the venous pedicle. Depending on the position of the arterial perforator relative to the skin paddle and the required pedicle length, the TCA pedicle may be designed in an antegrade or retrograde fashion (see Flap Harvest), although usually the antegrade pedicle is used. No attempt is made to look for the perforator as this may result in injury to the small vessels, encased within the fatty tissues of the flap. Several lymph nodes are reliably incorporated when harvesting the adipose tissue surrounding the pedicle. Some nodes are easily visible but smaller ones may not be. Superficial sensory nerves traversing the flap toward the upper chest are sacrificed. Caution must be sought not to transect the large lymphatic ducts both on right and left sides of the neck as to avoid developing a lymphocele or chyle leak. While the spinal accessory nerve lies deep to the flap and lateral to the area of dissection, the surgeon must be cognizant of its proximity and avoid injuring it.