Histopathology of malignant lesions of the penis.

Carcinoma of the penis is a relatively rare entity in the United States, accounting for less than 1% of all malignancies in male patients. It is largely a disease of elderly men, with age-specific rates increasing to a peak at about 80 years of age. By far the most common of these carcinomas arises from the squamous epithelium on the penile surface. The natural history of these lesions includes a transition from in situ to invasive forms with eventual metastasis to the regional lymph nodes. Associated with this are changes in the differentiated phenotype, which can be graded according to the degree of resemblance to normal squamous epithelium. Other uncommon epithelial malignancies such as basal-cell carcinoma and melanoma have also been reported. Finally, reflecting the heterogeneous composition of the penis, various sarcomas, including several vascular malignancies, have been seen. These lesions exhibit a range of malignant potentials consistent with their cellular derivation and degree of histologic differentiation.