LYMPHATIC DRAINAGE—EXTERNAL GENITALIA
A network of lymphatic anastomoses drains the external genitalia, the lower third of the vagina, and the perineum. Bilateral or crossed extension and drainage is common. The superficial femoral nodes are reached through the superficial external pudendal lymphatic vessels, although the superficial external epigastrics may also play a role. From the region of the clitoris, deeper lymphatic vessels may pass direct to the deep femoral nodes, particularly to Cloquet node in the femoral canal, or through the inguinal canal to the external iliac nodes. Cloquet node is thought to be the sentinel node between the superficial and deep inguinal/obturator lymph nodes. Sometimes, intercalated nodes may be encountered in the prepubic area or at the external inguinal ring. The lowermost portion of the vagina, like the vulva, may drain to the femoral nodes. This complex network of lymph nodes is clinically important, for these are the nodes to which cutaneous and vulvovaginal gland malignancies may drain. Regional lymph node dissections are routinely performed in the surgical treatment of vulvar cancer as the status of regional lymph nodes is essential for therapeutic planning and overall prognosis. Superficial nodes in the groin may also become enlarged when significant inflammation is present in vulvar structures (e.g., Bartholin gland infections).
The inguinal lymph nodes, both superficial and deep, lie within the
subcutaneous tissue roughly overlying the femoral triangle (“femoral” lymph
nodes). Lymphatic vessels tend to follow the course of veins draining a
particular region. The lymph nodes are arranged in groups or chains in close
relation to the vessels. The nodes found in this region are generally further
referred to as the superficial and deep inguinal lymph nodes.
The superficial femoral nodes are a group of nodes found in the loose,
fatty connective tissue of the femoral triangle between the superficial and deep
fascial layers. These nodes receive lymphatic drainage from the external
genitalia of the vulvar region, the gluteal region, and the entire leg,
including the foot: The saphenous nodes drain the lower extremities, whereas
the superficial circumflex nodes drain the posterolateral aspect of the thighs
and buttocks.
Afferent vessels from the lower abdominal wall and the upper superficial
aspects of the genitalia extend to the superficial epigastric nodes in the
abdominal wall above the symphysis. The superficial external pudendal nodes
drain the external genitalia, the lower third of the vagina, the perineum, and
the perianal region. Efferent lymphatic vessels from all the superficial femoral
nodes drain to the more proximal superficial inguinal (femoral) nodes, the deep
inguinal (femoral) nodes, and the external iliac nodes. Efferent lymphatics
from this group of nodes penetrate the fascia lata to enter the deep femoral nodes and represent the greatest concentration of lymph nodes in the
female.
A few constant nodes are usually associated with the deeper lymphatic
trunks along the femoral vessels. These may be situated on the mesial aspect of
the femoral vein, above and below its junction with the saphenous vein. The
highest of the deep femoral nodes lies within the opening of the femoral canal
(Cloquet or Rosenmüller node). The deep femoral nodes receive afferent
lymphatics directly or indirectly from the parts drained by the superficial femoral lymphatics and send efferent vessels to
nodes higher in the chain and to the external iliac nodes.
Knowledge of the lymphatic drainage of the perineum can be helpful in the
assessment and treatment of patients with vulvar cancers, where lymphatic
mapping and sentinel lymph node biopsy may be applied. The sentinel node(s) are
those nodes that directly drain the primary tumor and are thought to predict
the metastatic status of the upper nodes in the groin.
