Lymphatic mapping and sentinel node biopsy in early vulvar cancer

Approximately 1000 new cases of vulvar cancer are diagnosed annually in the United Kingdom. The overall five-year survival of about 50% is strongly related to the risk of nodal metastases, and spread is via embolisation to the inguinofemoral nodes. Most women present with surgically resectable disease and lymph node dissection is performed in almost all because of the risk of metastases unless tumour invasion is less than 1 mm. Tumour deposition in more than one node, multiple involved nodal sites and extracapsular spread of tumour are all adverse prognostic indicators, which is why FIGO staging includes histological assessment of the inguinofemoral nodes. Women with tumours approaching the midline undergo bilateral groin dissection, as the potential exists for spread to either side. In patients with laterally sited tumours, the involvement of contralateral nodes is rare if the ipsilateral nodes remain uninvolved, so for these small lateral tumours, ipsilateral node dissection is sufficient. If these nodes are found to be histologically positive, a contralateral groin dissection can be undertaken later. Currently, patients undergo complete block dissection of both the inguinal and femoral nodes. This is both a staging and potentially therapeutic procedure as less extensive node dissection is associated with increased recurrence rates. However, post-operative wound breakdown and infection is common and often prolongs hospitalisation, and pulmonary embolus has a high mortality. Anaesthesia over the medial thigh is frequent. The most significant long term complication is chronic lymphoedema and cellulitis of the legs, which occur in 24–70% of patients. Because less than 10% of all patients with clinical stage I disease will have lymph node involvement, younger patients tend to present earlier and have a five-year survival over 90%, complete inguinofemoral lymphadenectomy has been questioned in this group. Clinical assessment of groin nodes by palpation is notoriously inaccurate and ultrasonography is not capable of discriminating between enlarged normal nodes and metastatic deposits in nodes. The results of lymphography and monoclonal nucleotide imaging are also disappointing. Few data exist describing CT or MRI scanning and a preliminary study using positron emission tomography (PET) was only moderately successful in identifying metastatic inguinofemoral nodes in patients with carcinoma of the vulva. Ultrasound-guided fine needle aspiration cytology of groin nodes has been reported, with a sensitivity and specificity of 83% and 82%, respectively, for the identification of metastatic disease. This sensitivity is insufficient to adopt a ‘watch-and-wait’ policy as delayed dissection in the misclassified node positive patient has unknown prognostic consequences. In addition, prognostic factors related to the primary tumour such as lesion diameter, site, depth of invasion, differentiation, presence of vascular and lymphatic permeation, perineural invasion, host immune reaction, epidermal growth factor receptor expression, S-phase fraction and HER-2/neu status have all been correlated with the incidence of regional lymph node involvement. None has shown sufficient predictive value of metastases to obviate the need for nodal dissection. However, recent developments in the management of other malignancies such as cutaneous melanoma and carcinoma of the breast suggest selective dissection of a solitary node or nodes (i.e. the sentinel node biopsy) may reduce morbidity without compromising cure. In this review, we examine the concept of lymphatic mapping and sentinel lymph node biopsy in the management of early vulvar cancer.