Objectives: To examine the histologic features of p21 in penile tumors and to determine the role of p21 and p53 in the pathogenesis of this group of tumors.
Methods: The clinicopathologic features of 87 patients with penile tumors were studied. The expression of p53 and p21 proteins in 49 cases was investigated by immunohistochemistry.
Results: Of the 87 tumors studied, 84 represented primary penile tumors (72 malignant and 12 benign) and 3 represented secondary tumors (2 from bladder, 1 from nasopharynx). The primary malignant penile tumors included 66 surface carcinomas with squamous differentiation (92%), 3 cases of Paget disease (4%), 1 case of Bowen disease (1%), and 2 penile urethral squamous cell carcinomas (3%). The former group was subdivided into squamous cell carcinoma (n = 50), verrucous carcinoma (n = 8), basaloid squamous cell carcinoma (n = 3), adenoid squamous cell carcinoma (n = 3), spindle cell carcinoma (n = 1), and adenosquamous carcinoma (n = 1). The benign tumors were squamous cell papillomas (n = 10) and fibromatoses (n = 2). Expression of p21 and p53 was noted in 40% and 89%, respectively, of the 47 patients with primary surface penile carcinoma with squamous differentiation. Positive p21 and p53 expression was also seen in 2 cases of Paget disease. Staining for p21 was often weak and was found in the suprabasal region of carcinomas with squamous differentiation, while p53 expression was seen in the basal region of squamous cell carcinomas. Preinvasive lesions also showed p21 and p53 expression. An inverse correlation between p53 and p21 expression (p53(+)/p21(-) or p53(-)/p21(+)) was noted in half of the squamous cell carcinomas, 4 of 5 verrucous carcinomas, 2 of 3 basaloid squamous cell carcinomas, and in 1 spindle cell carcinoma. The other cases did not show this correlation.
Conclusions: Penile tumors had different histologic variants and p21/p53 expression patterns. Expression of p21 did play a role in some tumors and could be dependent or independent of p53 expression.