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Vulvar Surgery and Sentinel Node Mapping for Vulvar Cancer
In the past 100 years, the surgical approach to vulvar cancer has evolved from one of gynecologic oncology’s most morbid procedures to one of its least. The original approach included the radical en bloc resection of the vulva, groins, and iliac lymph nodes ( Fig. 4.1A ). Although this procedure greatly improved survival compared with earlier procedures, postoperative morbidity was exceedingly high as patients often experienced wound separation with prolonged healing, lymphedema, and long hospitalizations. The rationale for this radical approach was based on concern that tumor could potentially implant in the “skin bridge” between the primary lesion on the vulva and the lymph nodes in the inguinofemoral triangle. However, although in-transit tumor emboli were occasionally observed pathologically in the lymphatic channels of these en bloc resection specimens, true tumor implants were never encountered. Although recurrences in the skin bridge may occur, the short- and long-term morbidity of en bloc resection was felt to outweigh the risks of skin bridge recurrence, so surgeons moved to performing the primary resection and groin node evaluation(s) through separate incisions ( Fig. 4.1B ). Consequently the morbidity of wound separation and prolonged hospital stay significantly decreased, and oncologic outcomes were not compromised. Although separate incisions reduced wound complications, lymphedema remained a major postoperative long-term morbid condition, with 64% of women with vulvar cancer experiencing either grade 2 or grade 3 lymphedema after complete inguinofemoral lymphadenectomy. In an effort to reduce this morbidity, techniques for lymphatic mapping and sentinel nodes were pioneered and were proved to be valid for treating women with early-stage vulvar cancer ( Fig. 4.1C ). The adoption of lymphatic mapping and sentinel node biopsy for the treatment of vulvar cancer reduced the rate of lymphedema to less than 2%, again without compromising oncologic outcomes.
Evolution of the surgical management of vulvar cancer from (A) en bloc resection of vulva, groins, and iliac lymph nodes to (B) “triple” incision resection of primary tumor and inguinofemoral lymph nodes to (C) wide radical excision and sentinel lymph node biopsies.
Among the gynecologic malignancies, vulvar cancer is the fourth most common, behind uterine, ovarian, and cervical cancers and just ahead of vaginal cancer. Approximately 5% of all gynecologic malignancies will arise from the vulva. A woman’s lifetime risk of developing vulvar cancer is 0.3%; 2.5 new vulvar cancers occur per 100,000 women per year in the United States. The overall 5-year survival rate for all patients with vulvar cancer is 72%. When disease is limited to the vulva, the 5-year survival rate is 86.4% compared with 56.9% when disease has spread to regional lymph nodes and 17.4% when distant disease is present ( Table 4.1 ). Vulvar cancer remains a surgically staged disease, with International Federation of Gynecology and Obstetrics (FIGO) staging correlating well with the localized (stages I and II), regional (stage III), and distant (stage IV) disease states described earlier ( Table 4.2 ).
Table 4.1
Incidence and Survival for Vulvar Cancer Patients by Disease Extent
| Disease Extent | Percent of Cases | 5-Year Survival |
|---|---|---|
| Localized (confined to vulva) | 59% | 86.4% |
| Regional (spread to lymph nodes) | 30% | 56.9% |
| Distant (spread beyond lymph nodes) | 6% | 17.4% |
| Unknown/Unstaged | 5% | 56.2% |
Table 4.2
FIGO Staging for Carcinoma of the Vulva
| Stage | Description |
|---|---|
| Stage I | Tumor confined to the vulva |
| IA | Lesions ≤2 cm in size, confined to the vulva or perineum and with stromal invasion ≤1.0 mm, no nodal spread |
| IB | Lesions >2 cm in size or with stromal invasion >1.0 mm, confined to the vulva or perineum, no nodal spread |
| Stage II | Tumor of any size with extension to adjacent perineal structures (lower third urethra, lower third vagina, anus), no nodal spread |
| Stage III | Tumor of any size with or without extension to adjacent perineal structures (lower third urethra, lower third vagina, anus) with positive inguinofemoral lymph nodes |
| IIIA |
|
| IIIB |
|
| IIIC | With positive nodes with extracapsular spread |
| Stage IV | Tumor invades other regional (2/3 upper urethra, 2/3 upper vaginal), or distant structures |
| IVA | Tumor invades any of the following:
|
| IVB | Any distant metastasis including to pelvic lymph nodes |
FIGO, International Federation of Gynecology and Obstetrics.
Most (95%) vulvar cancers will have squamous histologic characteristics, with melanoma being the next most common subtype. Other subtypes of vulvar cancer that are seen infrequently include Bartholin gland carcinoma, adenocarcinoma arising in patients with Paget disease, basal cell carcinoma, verrucous carcinoma, and vulvar sarcomas. Finally, there are the exceedingly rare vulvar cancers found in limited case reports, which include endodermal sinus tumors, Merkel cell carcinomas, dermatofibrosarcoma protuberans, and malignant schwannomas ( Table 4.3 ).
Table 4.3
Differential Diagnosis of Vulvar Lesions
| Benign Lesions (Common) | Premalignant Lesions | Invasive Carcinomas |
|---|---|---|
|
|
|
There appear to be two independent pathways for the development of invasive squamous cell carcinoma of the vulva. The first tends to be associated with high-risk human papillomavirus (HPV) subtypes and accounts for 60% of vulvar cancers. The majority of the HPV-associated vulvar cancers harbor HPV-16 (80%–90%), with the remainder having either HPV-18 or HPV-33 subtype present. The HPV-associated vulvar cancers occur more frequently in younger women, many of whom report a prior history of genital warts or vulvar and/or cervical dysplasia. Immunosuppressed women are also more likely to follow this pathway to the development of vulvar cancer.
The other pathway, which affects older women, appears to be HPV independent. These cancers appear to be related to chronic inflammation. Many of these women will have had previous diagnoses of lichen sclerosis or squamous cell hyperplasia, and although the risk of development of invasive vulvar cancer in women with these lesions in 4.5%, neither lichen sclerosis nor squamous cell hyperplasia itself is considered a premalignant lesion. Women with HPV-negative tumors tend to have a worse prognosis compared with those with HPV-positive squamous cell carcinomas of the vulva.
Presentation, Diagnosis, and Workup
Presentation
Many patients with vulvar cancer will be asymptomatic, whereas others may complain of pruritus, particularly older patients with HPV-negative disease, because lichen sclerosis is often present in addition to invasive cancer. The classic presentation is a vulvar abnormality such as a plaque or mass. These lesions may be ulcerated, leukoplakic, or warty. Melanoma lesions may be darkly pigmented, but occasionally they can be amelanotic.
Diagnosis
The differential diagnosis of vulvar lesions ranges from benign lesions to invasive cancer (see Table 4.3 ). Vulvar biopsy must be performed on any suspicious lesions to confirm pathologic findings and to manage the condition appropriately. Health care professionals should have a very low threshold for performing biopsy on abnormal-appearing lesions on the vulva. In fact, one might consider the mantra “When in doubt, biopsy!” Because vulvar carcinoma can be multifocal in up to 5% of patients, multiple biopsies of abnormal-appearing areas must be undertaken.
A vulvar punch biopsy is the most commonly used procedure to arrive at a diagnosis. This procedure can be done in the clinic or office with local anesthesia. One must be sure to get an adequate sample that includes both dermis and underlying connective tissue to determine depth of invasion if invasive cancer is present.
After verbal or written consent has been obtained from the patient, the area around the lesion should be prepared with iodine or chlorhexidine. Once this is done, 2 to 3 mL of 1% to 2% lidocaine with or without epinephrine is injected around the lesion to form a wheal under the lesion. The biopsy specimen should be taken from the edge of the lesion as opposed to the center. It is ill advised to perform biopsy of the clitoris in the clinic because biopsy of this highly sensitive area will be poorly tolerated and should be performed with the patient under general anesthesia.
Use of a Keyes biopsy punch ( Fig. 4.2 ) is recommended, although a scalpel or scissors can be used. The Keyes biopsy punch is more likely to achieve adequate depth in the biopsy area, which is important if the lesion is invasive carcinoma. Although a punch biopsy ranges in size from 2 to 10 mm, generally 3 to 5 mm in size is adequate for a pathologic diagnosis of most lesions without causing too much discomfort or bleeding.
To perform the procedure, one presses the biopsy punch perpendicularly against the skin, holds it taut with the nondominant hand, and rotates with firm pressure. Ideally the rotation will be in one direction only (clockwise or counterclockwise) to avoid shredding the sample, but on occasion back-and-forth rotation is necessary. Once the instrument has reached adequate depth, the specimen is grasped with forceps and elevated, allowing for scissors or a scalpel to be used to transect the specimen at its base for pathologic processing.
Hemostasis is usually easily achieved with pressure or silver nitrate sticks. Monsel solution can also be used if bleeding is a bit brisker. Occasionally a suture will be needed to control bleeding, although this is rare.
Preoperative Workup
A careful physical examination with particular attention to the inguinofemoral groin nodes and local extent of disease should be performed. Once a pathologic diagnosis of invasive carcinoma with greater than 1 mm in depth of invasion has been made, preoperative imaging should be performed to rule out regional and distant disease. For squamous cell carcinomas, positron emission tomography–computed tomography (PET-CT) is favored because its sensitivity in detecting metastatic disease to the groins is greater than 90% ( Fig. 4.3 ). However, a CT scan or magnetic resonance imaging (MRI) is also acceptable because these modalities may have equivalent sensitivities and specificities to PET scan in assessing metastatic disease. Ultrasonography of the groins may also be considered for evaluation of metastatic disease to inguinofemoral lymph nodes. If there is concern for rectal or urethral invasion, MRI of the pelvis may be performed to assess tumor involvement of those structures. For women with adenocarcinoma arising in Paget disease, a complete workup for synchronous tumors must be undertaken because up to 30% of patients may have a second, noncontiguous primary carcinoma. The most frequently associated malignancies include breast, rectal, bladder or urethral, cervical, and basal cell carcinomas.
Preoperative Considerations
Anatomy
Primary vulvar carcinoma includes lesions of the labia majora, labia minora, clitoris, or perineum. For ambiguous lesions involving the vulvar structures and the anus or urethra, it is sometimes difficult to assign a primary site, and these lesions should be approached in a multidisciplinary manner. By convention, masses that include both the vulva and the vagina are considered primary vulvar carcinomas.
The vulva and lower third of the vagina have consistent lymphatic drainage to the inguinofemoral lymph nodes through a rich network of lymphatic channels ( Fig. 4.4 ). The anatomic boundaries of the inguinofemoral dissection (the femoral triangle) for vulvar cancer patients includes the inguinal ligament superiorly, the adductor longus muscle medially, and the sartorius muscle crossing laterally from the thigh medially to just above the knee ( Fig. 4.5 ). Although some texts describe direct lymphatic drainage from the clitoris to the pelvic lymph nodes (iliac or obturator), metastatic disease to the pelvic nodes in the absence of positive groin nodes is exceedingly rare. Routine dissection of pelvic nodes is not recommended as part of the primary operation for vulvar cancer (including clitoral lesions) unless bulky disease is noted at preoperative imaging.
The terms superficial and deep dissections have different meanings in surgical oncology. For example, in the treatment of a lower limb melanoma, superficial dissection refers to the groin nodes, whereas deep dissection refers to pelvic nodes. In gynecologic oncology, both terms refer to the inguinofemoral lymphadenectomy alone. Superficial dissection involves those nodes found between the Camper fascia and the fascia lata. The deep nodes are those along the femoral vessels, beneath the fascia lata and inguinal ligament. Cloquet’s node, just inside the fossa ovalis, is thought to be the transition from the superficial nodal bundle to the deep. Although there does not seem to be a risk of direct drainage to the pelvic nodes in the absence of positive groin nodes, there may be metastases from the vulva to the deep groin nodes in the absence of spread to the superficial nodes. It is therefore important to resect both superficial and deep nodes when performing a complete inguinofemoral lymphadenectomy because groin recurrences of 7% have been reported when only a superficial node dissection is performed.
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