Kevin R. Loughlin, MD, MBA
Penile cancer occurs rarely in the United States and Western Europe. In the United States, the incidence is 1 to 2 cases for every 100,000 individuals a year. In Western Europe, it is less than 1% of all male cancers. Risk factors include being uncircumcised, poor hygiene, history of human papillomavirus (HPV) infection, and smoking tobacco. HPV strains 16 and 18, in particular, put men at risk for penile cancer.
The presentation of penile cancer is variable. Patients may present with a penile mass or ulcer. In addition, some patients develop a red, velvety rash or foul-smelling discharge from beneath the foreskin.
Clinicians should have a low threshold to biopsy penile lesions. This can usually be done under local anesthesia. No treatment should be undertaken without a confirmation of an unequivocal permanent section pathology diagnosis. Urologists should not depend on a frozen section diagnosis done at the same time as a partial or total penectomy.
Challenges in Penile Tumor Staging
It is important to stage the primary tumor (T), the regional lymph nodes (N), and the presence of distant metastases (M). Several staging systems have been used through the years, but currently, the TNM system is the most widely used.1
The grade of the primary lesion is also considered in determining prognosis (Table 1
Table 1. Stages and Grades of Penile Cancer1
Magnetic resonance imaging (MRI) has emerged as the imaging modality of choice for the primary lesion.2
MRI is superior to computed tomography (CT) scans in the evaluation of the primary lesion because MRI has excellent soft tissue and spatial resolution. T2-weighted and gadolinium-enhanced T1-weighted images are the most useful in determining the local extent of the penile cancer.2
Determining lymph node status also is critical in establishing prognosis. Ravi reported that the 5-year survival rate declined from 95% for patients without nodal disease to 81% for patients with 1 to 3 positive nodes to 50% for patients with 4 or more positive nodes. CT, MRI, and fluorine 18 fluorodeoxyglucose (FDG) positron emission tomography (PET) and CT have all been used for the evaluation of inguinal lymph nodes.3
Ultrasound with fine needle aspiration cytology (FNAC) can be useful when there are palpable nodes on physical exam. The European Association of Urology supports the use of FNAC in this circumstance, noting sensitivity of 93%.4
CT imaging has been disappointing for the evaluation of inguinal lymph nodes. Horenblas et al reported a series of 14 patients and found that CT had a sensitivity of 36% and a specificity of 100%, but was unable to detect occult metastases in groins without palpable nodes.5
MRI results in evaluation of inguinal nodes have not been superior to CT.6
Due to the limitations of standard CT and MRI imaging of the inguinal nodes, FDG PET/CT has gained increasing acceptance as the study of choice for inguinal node imaging. Schlenker et al reported a prospective study of 35 patients with penile cancer and found that the FDG PET/CT had a sensitivity of 88.2% and a specificity of 98.1%, with a positive predictive value of 93.8% and a negative predictive value of 96.3%.7
Graafland et al also utilized FDG PET/CT for penile cancer staging and reported a sensitivity of 91%, a specificity of 100%, and a diagnostic accuracy of 96% in identifying inguinal/pelvic node involvement.8
The technique of sentinel node biopsy was introduced by Cabanas in 1977 in an attempt to sample the first landing site of inguinal node metastatic spread.9
His rationale was that this node or cluster of nodes located around the superficial epigastric vein was predictive of the status of the remainder of the inguinal nodes. However, the lymphatic drainage of the penis is variable and several authors have reported false negative rates of 10% to 25%.10-12
Therefore, this technique, although theoretically attractive, has fallen into disfavor.
To try to improve accuracy, dynamic sentinel lymph node biopsy (DSLNB) was introduced. This technique involves mapping the penile lymphatic drainage with blue dyes and/ or radiotracers.13
The results of DSLNB appear to be highly variable and user dependent; some results were no better than standard lymph node biopsy.14,15