Fig. 1

EcPV2 associated gross lesions. Representative images of EcPV2 associated gross lesions: a.) Depigmented plaques and hyperplastic epithelium of the penis shaft, developing up to the glans penis are visible. Histologically these lesions were diagnosed as benign hyperplasia (#19). b Two depigmented plaques can be seen on the penis shaft (white arrow) and one on the glans penis, where a small wart-like lesion (black arrow) is also visible, which was histologically diagnosed as papilloma. The depigmented plaques on the shaft (white arrow) were diagnosed as carcinoma in situ (#6). c The whole penis has depigmented thickened epithelium. Two wart-like lesions are also visible (black arrows), which were histologically diagnosed as papillomas (#13). On the penis shaft there is a small ulcerated area (white arrow), which is the second recurrence of a surgically removed SCC. Histologically this lesion was classified as early SCC (#5). Both lesions of this horse were included in this study, listed as separate cases. d The whole penis shows depigmented and thickened epithelium. There is a massive proliferation/mass on the glans penis. Histologically this tumoural lesion was diagnosed as SCC (#3)