Carcinoma cuniculatum: a distinctive variant of penile squamous cell carcinoma: report of 7 cases.

We are reporting a peculiar variant of penile squamous cell carcinoma (SCC) characterized by its peculiar deeply penetrating and burrowing pattern of growth. This low grade, verruciform penile neoplasm is similar to the plantar epithelioma cuniculatum originally described by Ayrd in 1954. Clinical and pathologic features of 7 patients are presented. There were 7 partial penectomies and 4 bilateral inguinal node dissections. The mean patient's age was 77 years. Grossly, the tumors were white to gray, exo-endophytic, and papillomatous with a cobblestone or spiky appearance. All cases affected the glans and extended to coronal sulcus and foreskin (average size was 6.3 cm). The hallmark of the lesion was noted on cut surface where there were deep tumoral invaginations forming irregular, narrow, and elongated neoplastic sinus tracts connecting the surface of the neoplasm to deep anatomic structures. The neoplasm invaded through lamina propria and corpus spongiosum and grew along the loose connective tissue of Buck fascia to involve the tunica albuginea and corpora cavernosa (average depth was 32 mm). Deeply invasive keratin filled cysts or crypts, on serial sections, showed to be connected to the surface tumor. Fistulization to the skin was also noted. Microscopically, the lesions corresponded to well-differentiated carcinomas with bulbous front of invasion. There were focal areas of higher histologic grade and more infiltrative and jagged borders in 4 cases. Inguinal nodes were negative in 4 patients in which groin dissection was performed. Carcinoma cuniculatum is a variant of penile SCC with distinctive growth pattern and should be distinguished from other verruciform tumors such as the verrucous, papillary, and warty carcinomas. Unlike most subtypes of penile SCCs and despite the deep invasion, none of the tumors showed groin or systemic dissemination at time of diagnosis.