Basaloid squamous cell carcinoma of the penis with papillary features: a clinicopathologic study of 12 cases

There are 3 distinct variants of penile squamous cell carcinoma frequently associated with human papillomavirus (HPV): basaloid, warty-basaloid, and warty carcinomas. Considering the high incidence rates of penile cancer in some countries, a large international study was designed to evaluate the presence of HPV, its genotype distribution, and its association with histologic types of penile cancer. In this international review of >900 cases, we found a group of highly distinct papillary neoplasms composed of basophilic cells resembling urothelial tumors but frequently associated with HPV. Macroscopically, tumors were exophytic or exoendophytic. Microscopically, there was a papillomatous pattern of growth with a central fibrovascular core and small basophilic cells lining the papillae. Positivity for HPV was present in 11 of 12 tumors (92%). Single genotypes found were HPV-16 in 9 tumors and HPV-51 in 1 tumor. Multiple genotypes (HPV-16 and HPV-45) were present in another case. Overexpression of p16 was observed in all cases. Uroplakin-III was negative in all cases. The differential diagnosis was with basaloid, warty-basaloid, warty, and papillary squamous cell carcinoma and with urothelial carcinomas. Local excision (4 cases), circumcision (3 cases), or partial penectomy (5 cases) were preferred treatment choices. Tumor thickness ranged from 1 to 15 mm (average, 7 mm). Two patients with tumors invading 11 and 15 mm into the corpus spongiosum developed inguinal nodal metastasis. Of 11 patients followed up (median 48 mo), 7 were alive with no evidence of metastatic disease, 3 died from causes other than penile cancer, and another died postoperatively. This morphologically distinct tumor probably represents a papillary variant of basaloid carcinomas (papillary-basaloid carcinomas). Unlike typical basaloid carcinomas, the overall prognosis was excellent. However, deeply invasive tumors were associated with regional nodal metastasis indicating a potential for tumor-related death.