To my knowledge, only 45 cases of carcinoma appearing in smallpox vaccinations are in the literature. Basal cell carcinoma appeared in a smallpox scar 50 years after vaccination in a 64-year-old man. Significant evaluation of their relationship at this time is impossible. Whether this is a casual occurrence or a definite sequela to smallpox vaccination cannot be determined from present knowledge.
Riley KA. Basal Cell Epithelioma in Smallpox Vaccination ScarReport of a Case. Arch Dermatol. 1970;101(4):416-417. doi:10.1001/archderm.1970.04000040038008