Continuing Education Activity

Lymph node dissection is a surgical procedure in which the lymph nodes are dissected, and a sample of tissue is checked for the presence of cancer under a microscope. It is an operation usually performed as part of the surgical management of malignant tumors and can be further divided into regional lymphadenectomy and radical lymphadenectomy. This activity reviews and explains the role of the interprofessional team in evaluating and managing patients who undergo lymph node dissections.

Objectives:

• Identify the indications for lymph node dissection.
• Review the complications associated with lymph node dissection.
• Describe the equipment for lymph node dissection.

Introduction

Lymph node dissection, also known as lymphadenectomy, is a surgical procedure in which the lymph nodes are dissected, and a sample of tissue is checked for the presence of malignancy under the microscope. It is an operation usually performed as part of the surgical management of malignant tumors. Lymph node dissection can be further divided into regional lymphadenectomy, where there is a removal of some of the lymph nodes in the tumor area (inguinal, femoral, iliac, epitrochlear, cervical, popliteal, retroperitoneal, or axillary lymph node groups) and radical lymphadenectomy where there is a dissection of most or all of the lymph nodes in the tumor area. Finding cancer cells in the lymph nodes is associated with a higher risk of metastasis to other parts of the body and portends a poorer prognosis.

The region of lymph node dissection depends on the site of involvement. The four most common dissection sites are axillary lymph nodes (for breast cancer), inguinal lymph nodes (for penile, anal, and vulvar cancers), cervical lymph nodes (for head/neck cancers and thyroid cancers), and retroperitoneal lymph nodes (for testicular and ovarian cancers).[1][2][3]

Anatomy and Physiology

The lymphatic system, or lymphoid system, is a part of the circulatory system and the immune system. It consists of the primary lymphoid organs and the secondary lymphoid organs. The thymus and the bone marrow constitute the primary lymphoid organs. Both of them are involved in the production and early clonal selection of lymphocytes. Bone marrow is responsible for the production and maturation of B cells and the production of T cells. B cells travel from the bone marrow to the secondary lymphoid organs in search of pathogens. T cells, on the other hand, travel from the bone marrow to the thymus, where their maturation takes place. The thymus, as mentioned earlier, is a primary lymphoid organ. It provides an environment for the development and maturation of T cells. In addition, one of the most important roles of the thymus is the induction of central tolerance.

Thymic stromal cells allow the self-tolerance of T cells. The secondary lymphoid organs include lymph nodes, spleen, and mucosa-associated lymphoid tissues. The spleen consists of red and white pulp. In the red pulp are stored half of the body’s monocytes. On the other hand, antibodies are synthesized in the white pulp. The spleen removes antibody-coated bacteria and antibody-coated blood cells from circulation. Lymph nodes consist of the afferent and efferent lymph vessels, capsule, sinus, nodule, and cortex. Lymph nodes allow antigens to interact with the lymphocytes. As mentioned above, mucosa-associated lymphoid tissues are secondary lymphoid structures. These are present within the mucosal surfaces of almost any organ, but especially those of the digestive, genitourinary, and respiratory tracts. For example, Peyer’s patches, which are mucosa-associated lymphoid tissues of the small intestine, sample passing antigens and expose them to underlying B and T cells.

The lymphatic vessels are thin-walled vessels that conduct lymph between different parts of the body. The lymph capillaries are responsible for the absorption of interstitial fluid from the tissues. Lymph vessels propel the absorbed fluid into larger collecting ducts, and it finally returns to the bloodstream via one of the subclavian veins.[4][5][6][7][8][9] 

The lymphatic system has many functions. First of all, it collects fluid that drains from cells and tissues and returns it to the bloodstream. Secondly, it absorbs fats from the digestive tract: lymph includes fluids from the intestines that contain fats and proteins and transports it back to the bloodstream, and finally, it protects against foreign antigens.[10]

Indications

Lymph nodes are the most usual sites of solid tumor metastases.[11] Sir Berkeley Moynihan, a famous British surgeon, once remarked that "the surgery of cancer is not the surgery of organs; it is the surgery of the lymphatic system." The lymphatic system is one of the main routes through which many types of cancers spread, and the adjacent lymph node is most vulnerable to be involved. Lymph node dissection is usually performed because of the tendency of many types of malignant tumors to produce lymph node metastasis at an early stage in their natural history. There are many types of cancers like breast cancer, colorectal cancer, melanoma, thyroid cancer, head, and neck cancer, gastric cancer, and lung cancer, which have a predictable route of metastasis hence removing lymph nodes and checking it microscopically for possible cancer involvement would be beneficial to assess the spread of cancer.[12]

Indications for regional or radical lymphadenectomy depend on position and type of malignant tumor. The four most common examples of lymphadenectomy are radical neck dissection for thyroid as well as head and neck cancers, axillary lymph nodes for breast cancer, total mesorectal excision for rectal cancer, and D2 lymph node dissection for gastric cancers.

Contraindications

There are no absolute contraindications to lymph node dissection. However, lymphadenectomy is not usually performed in patients with distant metastasis.

Equipment

Surgical instrument sets depend on the procedure for which lymph node dissection is performed. The operating room, as well as anesthesia equipment, is necessary. Sometimes laparoscopic method may be a choice by surgeons like in laparoscopic distal gastrectomy with D2 lymphadenectomy. In this case, a laparoscopic tower, as well as laparoscopic instruments (laparoscope, needle driver for suturing, trocars, bowel grasper), are needed for this surgical procedure.[13]

Personnel

Depending on the type of surgery, either general surgeons or other specialized surgeons may perform lymph node dissection. Breast surgeons usually perform axillary lymphadenectomy. Gynecologic oncologists are specialists for pelvic and retroperitoneal lymph node dissection when patients undergo total abdominal hysterectomy with bilateral salpingo-oophorectomy for gynecological malignancies. Urologists perform retroperitoneal lymph node dissections for testicular cancers and pelvic lymph node dissections for penile cancers. Also, otorhinolaryngologists are surgical specialists who perform cervical lymph nodes dissection in patients with thyroid and head and neck cancer.

Preparation

All patients are hospitalized one day prior to surgery. Routine blood tests as well as chest radiography are ordered. Informed consent is obtained by surgeons before the operation. Further preparation depends on the kind of surgery. Patients who are prepared for colorectal operation with total mesorectal excision may be asked to take an enema the evening before surgery, to empty the bowels.

Technique or Treatment

Depending on the location of lymph nodes, lymphadenectomy can be carried out as either open surgery or laparoscopic surgery. In the operation of radical open inguinal lymphadenectomy for penile carcinoma, the patient is supine with legs fixed in moderate external rotation. Having as anatomical reference points the pubic symphysis and anterior superior iliac spine, a 10-cm horizontal skin incision is performed 2 cm above the inguinal crease. The femoral triangle apex is reached by dissecting the lower skin flap at Scarpa fascia level until 10 to 12 cm below the incision. The great saphenous vein (GSV) is severed and isolated between ligatures. The surgeon continues dissection of GSV and its branches at its insertion into the common femoral vein (CFV).

Surgical specimen, which includes lymphatic nodes between the sartorius and adductor longus muscles as well as fascia covering these muscles is removed close to femoral vessels and sent to the laboratory to be assessed for the presence of cancer cells. To avoid lymph drainage, all subcutaneous tissues along medial, distal, proximal, and lateral margins are sutured.[14]

An axillary lymph node dissection (ALND) for breast cancer is performed by an incision that measures approximately 2 inches across the patient's axilla. Lymph nodes located below the lower edge of the pectoralis minor muscle (level I) as well as lymph nodes located directly under the pectoralis minor muscle (level II) are removed. A small drain may be placed to avoid post-operative complications.[15] Retroperitoneal lymph node dissection (RPLND) is used for testicular cancers and retroperitoneal malignancies and can be performed open or laparoscopic. Open surgery requires a 6 to 9-inch incision to open the abdomen. The inferior mesenteric artery (IMA) is usually sacrificed to aid dissection. Ligation of the lumbar veins and arteries is performed as they disappear to the psoas muscle. Care should be made to identify and preserve the left ureter in this plane of dissection.[16][17] 

Total mesorectal excision (TME) is a common surgery used in the treatment of colorectal cancer in which the patient is placed in the modified lithotomy position. The aim of this procedure is the en bloc resection of rectal cancer with a complete pararectal lymphadenectomy as contained in the mesorectum, with a rectal fascia intact. TME may be performed as an open, laparoscopic, or robotic operation with comparable oncological results.[18][19] Transanal endoscopic total mesorectal excision (Ta-TME) is another surgical option that has been receiving considerable attention in the treatment of colorectal cancer. In this technique, dissection of the rectum through the anal canal is performed laparoscopically in a caudal-to-cephalad direction.[20]

A neck dissection is a surgery to remove cervical lymph nodes from the neck for the purpose of cancer treatment. Macfee incision, which comprises of two horizontal parallel incisions, is a commonly used incision for neck dissection. The platysma muscle is identified and raised to perform neck dissection. Neck dissection is performed depending on the extent and involvement of vital structures. Pectoralis major myocutaneous flap or temporalis flap and skin graft are used for the reconstruction.[21]

Complications

Although lymph node dissection is an important part of cancer assessment and treatment, as with any other surgical procedure, complications can occur. Complications depend on the site and extent of the dissection.[22] Common complications include pain, numbness, and surgical wound infections. Patients may also develop lymphedema, which is swelling and edema of the arms or lower limbs, which happens due to the accumulation of lymph in the interstitial tissue, causing the affected area to feel heavy and swollen.[23]

Depending on the type of surgery and lymph node dissection, various other complications may occur. Pancreatic fistula, hemorrhage, bile duct injury, and chylous fistula are complications specifically related to lymph node dissection performed in gastric cancer surgical operations.[24] Also, the dissection of more than 14 retroperitoneal lymph nodes is an independent risk factor for the occurrence of postoperative complications such as deep vein thrombosis, extra operative site infections, lymphocytes, relaparotomy, febrile morbidity, and wound dehiscence in patients undergoing surgical staging for endometrial carcinoma.[25]

Complications specifically related to axillary lymph node dissection include lymphedema, paresthesia, seroma, lymphocele, hematoma, lymphatic fibrosis, and axillary vein thrombosis.[26][27] Furthermore, central and lateral cervical lymph node dissection for thyroid cancer is associated with severe morbidities such as intra-operative and post-operative bleeding, damage to the facial nerve or vagus, and respiratory distress.[28]

Clinical Significance

The role of the human lymphoid system in human physiology remains an intriguing issue. Although the likelihood of lymph node metastasis is higher in large primary tumors for most solid organ malignancies, there are also many patients with large tumors who do not develop lymph node metastasis. On the other hand, there are patients with small or early-stage primary tumors who develop an extensive regional nodal disease. In addition, the presence of metastasis in lymph nodes remains a prognosticator of patient outcomes.[29] For many cancers such as prostate, testicular, breast, gynecologic, and head, and neck cancers, as well as melanoma lymph node dissection, it provides the most accurate and reliable method for evaluation and management of metastasis.[30][31]

Enhancing Healthcare Team Outcomes

Patients undergoing lymph node dissection require an inter-professional team approach. General surgeons and other specialized surgeons conduct these surgeries. Pathologists will then look for cancerous cells within that lymph node. Medical and radiation oncologists, anesthesiologists, radiologists, and other healthcare professionals are also part of this interdisciplinary team who help diagnose, treat, and follow these cancers.