Chi_Principles and Practice of Gynecologic Oncology 8e

12 SECTION 2 ■ Vulvar Cancer

have bilateral lymph drainage. Dye studies have demonstrated that vulvar lymphatic channels do not extend laterally to the labiocrural folds and do not cross the midline, unless the site of dye injection is at the clitoris or perineal body (1). However, under specific cir cumstances (eg, blockage of lymph channels, prior vulvar or groin surgery, or large groin metastases), contralateral lymphatic drain age may occur (2,3). The inguinal nodes are subdivided into the superficial and deep inguinal nodes. The superficial inguinal LNs are located anteri orly within the femoral triangle along the saphenous vein and its branches ( Figure 2.2-1A-C ). They drain the perineal genitalia, anus, perianal skin, anterior abdominal wall below the umbilicus level, and round ligament of the uterus. The deep inguinal LNs are lo cated in the femoral canal, medial to the femoral vein. They drain the lower extremity and also receive drainage from the superficial inguinal nodes and clitoris. Both the superficial and deep inguinal nodes drain into the external iliac nodes. The first LN to receive drainage from the vulva is called the sen tinel lymph node (SLN). It can be identified by lymphatic mapping techniques, for example, the lymphoscintigram. The sentinel node is frequently found on the medial side of the femoral vein and su perior to the adductor muscle. The lymphatics can drain from the sentinel node and other inguinofemoral LNs into the external iliac, common iliac, and aortic LNs. N atural H istory (P atterns of S pread ) Vulvar cancer can spread in three ways: by local growth and di rect invasion of adjacent organs (eg, vagina, anus, or urethra), by lymphatic spread to the inguinofemoral LNs, and by hematog enous spread to distant sites (eg, lung or liver). Risk factors for inguinofemoral LN metastases include tumor size, tumor stage, grading, depth of stromal invasion (DOI), and vascular and lym phovascular space invasion (4). Nodal metastases are rare if DOI is less than 1 mm, but the risk rises sharply with DOI greater than 1 mm. In addition, Dabi et al found that the presence of lichen scle rosus (LS) is a risk factor (5). HPV is widely accepted as a posi tive prognostic factor and seems to be associated with less groin involvement, but evidence for the latter is scarce (6-8). Pelvic LN metastases are observed in 18.5% of patients with inguinofemoral metastases (9). In the absence of inguinofemoral metastases and/or

Vascular Anatomy and Neurologic Innervation

The vulva has a rich blood supply derived primarily from the in ternal pudendal artery, which arises from the anterior division of the internal iliac (hypogastric) artery, and the superficial and deep external pudendal arteries, which arise from the femoral artery. The internal pudendal artery exits the pelvis and passes behind the ischial spine to reach the posterolateral vulva, where it divides into several small branches to the ischiocavernosus and bulbocaverno sus muscles, the perineal artery, artery of the bulb, urethral artery, and dorsal and deep arteries of the clitoris. Both external pudendal arteries travel medially to supply the labia majora and their deep structures. These vessels anastomose freely with branches from the internal pudendal artery. Multiple spinal cord levels are involved in the innervation of the vulva. The ilioinguinal nerve from L1 and the genital branch of the genitofemoral nerve (L1-2) innervate the mons pubis and the an terior part of the labia majora. Either of these nerves may be easily injured during pelvic lymph node (LN) dissection, with resulting paresthesias. The pudendal nerve (S2-4) enters the vulva parallel to the internal pudendal artery and gives rise to several branches that innervate the lower vagina, labia, clitoris, perineal body, and their supporting structures. Groin Anatomy and Lymphatic Drainage The femoral triangle is bordered superiorly by the inguinal liga ment, laterally by the medial border of the sartorius muscle, and medially by the adductor longus muscle. The roof of the femoral canal is the fascia lata, and the floor consists of the pectineus, ilio psoas, and adductor longus muscles. The femoral triangle encom passes several structures: the femoral artery and vein, the femoral nerve, and the femoral canal. The fascia lata has a crescent-shaped opening called the fossa ovalis or the saphenous opening, which is covered by the cribriform fascia. The great saphenous vein pierces through the cribriform fascia, accompanied by several superficial branches from the femoral artery and lymphatics. The femoral ar tery and vein and the femoral canal are contained within the fem oral sheath. The lymphatics of the vulva run anteriorly through the labia majora, turn laterally at the mons pubis, and drain primarily into the superficial inguinal LNs. The clitoris and the perineal body

Superficial epigastric vein

Inguinal ligament

Superficial circumflex iliac vein

Femoral vein

Sentinel lymph nodes

Lateral accessory saphenous vein

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Great saphenous vein

Opening of Hunter canal

A ❚ Figure 2.2-1. Lymphatic anatomy in the groin. A Some possible locations of sentinel nodes.