Contact Spread of Carcinoma of the Skin

The case history of a patient with basal cell carcinomas on the thumb and the ear is presented. The patient had burnt the thumb 17 months prior to presentation and the burn had never fully healed. He volunteered that he habitually slept on his side with the thumb in contact with the ear. The histological features of the two lesions were identical. Similar reported cases and the experimental data on basal cell tumour implantation are reviewed in an attempt to prove that this case is one of implantation metastasis. Some of the evidence is strongly in favour of this possibility, but the verdict must be one of "not proven".

A case of simultaneously occurring basal cell carcinomas with identical histology is presented. In the light of published clinical cases and experimental data, an attempt has been made to prove that one lesion was an implantation metastasis of the other. The available evidence allows only the Scottish verdict of "not proven" to be made. The points for and against a diagnosis of implantation metastasis are listed. Points in favour are the long history of contact, the rarity of basal cell carcinoma of the thumb, the histological features of the tumours, the unusual time interval if the tumour was a "burn cancer", and the suitable "culture medium" for metastasis following the burn. Points against such a diagnosis are the occurrence of many histologically similar basal cell carcinomas in a series of ten cases, the possibility that the tumour was a burn cancer, the experimental difficulty in transplanting basal cell carcinomas, and the experimental evidence that stroma is required to transplant basal cell carcinomas successfully.