Verrucous carcinoma of the skin: a report on 5 Japanese cases.

Verrucous carcinoma (VC) of the skin is relatively rare. The author reports 5 Japanese cases of VC of the skin. The age ranged from 63 to 91 years with a median of 70 years. The locations were hand in 1 case, lip in 1, face in 1, and foot sole in 2. The size ranged from 0.8 cm to 30 mm with a median of 1.5 cm. Grossly, all the cases showed elevated verrucous tumors. Histologically, the tumors were composed of squamous epithelial cells with minimal cellular atypia arranged in a verrucous pattern. One case showed koilocytosis. Neutrophilic abscesses were seen in 3 cases. Microinvasion was recognized in 2 cases. Focus of less differentiated squamous cell carcinoma was seen in the VC in 1 case. Actinic karatosis or squamous cell carcinoma in situ contiguous to VC was seen in 1 case. Definite precedent lesions were not recognized in any of the cases. Immunohistochemically, VCs of the skin were negative for human papilloma virus antigens in the 2 cases examined. p53 protein was expressed in all the VCs and accentuated in the basal and microinvasive parts. The Ki-67 antigen was also expressed in all the VCs, and it was mainly observed in the basal and microinvasive areas. These findings suggest that (1) VC of the skin can occur in any skin sites, (2) VC of the skin can transform into less differentiated squamous cell carcinoma, and (3) VC of the skin may be associated with squamous cell carcinoma in situ.