Groin dissection is a procedure performed in the treatment of a number of cutaneous malignancies, including melanoma, squamous cell carcinoma, Merkel cell carcinoma, and other skin appendage tumors metastatic to that nodal basin. Other primary tumor sites potentially metastatic to the superficial groin include the vulva, anus, and penis. Visceral sites potentially metastatic to pelvic nodes include cervix, endometrium, prostate, and bladder. This chapter deals specifically with lymphadenectomy for metastatic disease to regional nodes, and does not specifically address resection of benign or malignant soft-tissue neoplasms of the groin region. Furthermore, it focuses on the technical details of open surgical lymphadenectomy, rather than the minimally invasive laparoscopic approach.

Through the 1980s, perhaps the most common indication for groin dissection was in the elective setting for intermediate thickness melanomas of the trunk or lower extremities. However, the overall incidence of groin dissection for melanoma has decreased dramatically over the last 20 years. In the absence of prospective data to support routine application of elective lymph node dissection, and with the advent and subsequent widespread application of sentinel lymph node biopsy, the principal indications for this procedure in melanoma have evolved toward either selective or completion lymph node dissection in patients with positive sentinel nodes, or therapeutic lymph node dissection in those with clinically positive regional nodes, both in the absence of known distant metastatic disease. The procedure may be unilateral, or, in the case of midline primary tumors, bilateral. The procedure may entail removal of inguinofemoral nodes in the superficial groin, that is, those nodes superficial to the inguinal ligament, the ileo-obturator nodes deep to the inguinal ligament in the pelvis, or both.

Although never formally confirmed in the context of a prospective randomized trial, in the absence of distant disease, few would argue with the therapeutic value of complete lymph node dissection in patients with clinically positive nodes. A substantial proportion of these patients are cured with no further treatment beyond complete surgical resection. On the other hand, the therapeutic value of completion lymph node dissection in patients with a positive sentinel lymph node from melanoma is unknown, and is currently the focus of an ongoing prospective randomized study, the Multicenter Selective Lymphadenectomy Trial II.

In patients with known distant metastatic disease, palliative groin dissection may be indicated to achieve control of symptomatic regional disease in the nodal basin. Given the substantial morbidity of the procedure, groin dissection to control potential future symptoms in the presence of known systemic metastases should be done sparingly if at all, and if so, only on a case-by-case basis.

The anatomy of the groin is quite constant. The superficial groin is defined by the femoral triangle, consisting of the sartorius muscle laterally, the adductor magnus and pectineus muscles medially, and the inguinal ligament superiorly. The transition from external iliac to common femoral vessels occurs as they traverse the femoral canal from the pelvis into the thigh. Medially in the femoral canal, there are lymphatics containing Cloquet’s lymph node. Proceeding laterally, we encounter the common femoral vein, the common femoral artery, and more laterally, the common femoral nerve. The saphenous vein enters the inferior apex of the femoral triangle at the junction of the adductor magnus and sartorius muscles, and courses through the middle of the triangle, through the fossa ovalis, to drain into the common femoral vein at the saphenofemoral junction. Branches of the saphenofemoral junction include the lateral femoral circumflex, medial femoral circumflex, external pudendal, superficial circumflex iliac, deep circumflex iliac, and superficial epigastric veins. The exact anatomy and caliber of these veins varies from one patient to the next; most of these veins have corresponding arteries. As all of these small vessels traverse the lymphadenectomy
specimen, each requires division at both the periphery and the center of the lympha-denectomy.

Working cephalad, just above and deep to the inguinal ligament, the common femoral vessels become the external iliac vessels. Immediately deep to the inguinal ligament, the deep circumflex iliac artery and vein course laterally, while the inferior epigastric artery and vein arise medially to course along the undersurface of the rectus abdominus muscle. Proximal to these two vessels, there are no further named branches of the external iliac vessels. Working cephalad further, we encounter the bifurcation of the common iliac into the internal and external iliac vessels. The internal iliac vessels branch widely. The first branch is the superior gluteal, which traverses the sciatic notch to the buttock, and represents an important source of collateral circulation to the lower leg in the event of external iliac interruption. Other branches include the inferior and superior vesical, the internal pudendal, the obturator, and the superior and middle hemorrhoidal vessels. Not all of these branches can be traced out in every pelvic lymphadenectomy. Traversing the triangle between the external and internal iliac vessels is the obturator nerve, which joins the obturator artery and vein to exit the obturator foramen. Medial to the deep pelvic node compartment is the peritoneum and its contents, and the retroperitoneal structures of the ureter, rectum, and bladder. The lateral aspect is bordered by the endopelvic fascia.

If pelvic lymphadenectomy (ileo-obturator lymphadenectomy) is to be performed, and this is anticipated ahead of time based on imaging studies, Cloquet’s node need not be sampled, and the entire lymph node package, both superficial and deep, can be removed in continuity, by extending the incision cephalad and dividing the inguinal ligament (see below). If the superficial groin contents have been removed previously, then the pelvic nodes can be approached through a suprainguinal skin crease-type incision. That incision should be low enough to enable access to the distal most external iliac nodes, and should be long enough to provide adequate exposure and access to the more proximal pelvic nodes.

If Cloquet’s node is positive on frozen section, and the deep pelvic portion of the lymph node dissection is to be done in continuity, the skin incision is extended cephalad, up toward the a point 3 to 4 cm medial to the anterior superior iliac as described above. The skin and subcutaneous tissues are divided. The fascia of the external oblique muscle is divided lateral to the rectus abdominus muscle in the direction of its fibers, bringing that incision down toward the inguinal ligament at the level of the femoral vessels. Prior to dividing the inguinal ligament, the retroperitoneum is entered. This is done by grasping the internal oblique muscle lateral to the rectus muscle, and dividing it in the direction of the previous incision. An areolar plane is entered just deep to the transversalis fascia. Great care is taken at this point not to violate the peritoneum. The peritoneum and its contents are then bluntly dissected off the undersurface of the transversalis muscle laterally and the femoral vessels in the depth of the incision. We prefer to retract
the inferolateral aspect of the abdominal wall with Kocher clamps to facilitate this access to the retroperitoneum. The incision is then developed more cephalad, dividing the abdominal wall muscles to the level of the anterior superior iliac spine, and caudad down toward the femoral canal. A finger is placed through the femoral canal to protect the femoral vessels as the ligament is divided at this level. At this point, complete exposure of the pelvis can be achieved, as the peritoneum and its contents is bluntly dissected and retracted superomedially. We find that a multiblade self-retaining retractor (Bookwalter, Thompson) at this point is invaluable to provide and maintain exposure (Fig. 12). Deep Richardson-type blades are placed to retract the peritoneum superiorly and medially, to retract the bladder medially, and to retract the abdominal wall laterally. This generally affords excellent exposure to the lower retroperitoneum and pelvis. As with all self-retaining retractors, care must be taken at this point to avoid sustained pressure on the femoral nerve, to prevent postoperative nerve palsy.