FIG. 2.

Gross and histological characteristics of papillomas and malignant tumors on vaccinated and control rabbits. (A) Papillomas on a vaccinated rabbit. The lesion shows limited amounts of horny tissue on the top of the papillomas. The photograph was taken 9 weeks following the first vaccination. Bar, 1.5 cm. (B) Carcinoma on a nonvaccinated rabbit. Cancer shows invasive growth into adjacent tissue with ulcerating surfaces and necrosis in the middle of the carcinoma. Bar, 2.0 cm. (C) Papilloma on a vaccinated rabbit showing histological characteristics of papillomavirus-infected benign epithelial lesion. Magnification, ×15. (D) Carcinomas showing tumor cells in dermis. Magnification, ×100. Hematoxylin and eosin stain was used in panels C and D.