Four basal and one squamous cell carcinomas and a single instance of a malignant melanoma arising in vaccination scars have occurred in five southern California patients. Sun exposure on a previously scarred skin was the main etiological factor in the development of the basal and squamous cell tumors. Sun exposure was probably unimportant in the case of the melanoma because of the short time interval between vaccination and the development of the tumor.
Reed WB, Wilson-Jones E. Malignant Tumors as a Late Complication of Vaccination. Arch Dermatol. 1968;98(2):132-135. doi:10.1001/archderm.1968.01610140030005