Abstract
A spayed 14-year-old female domestic shorthair cat presented with a squamous cell carcinoma of the nasal planum and was treated with intralesional chemotherapy. During nasal infiltrations with cisplatin mixed with the cat's own serum, a new carcinomatous lesion developed at the medial canthus of the right eye, which was also treated using intralesional chemotherapy. Two months after the treatment course, the cat developed a new mass at the site of the eyelid chemotherapy, which was diagnosed as a soft tissue sarcoma. At the owner's request, the tumour was marginally excised, but it recurred after 10 months. No lung or lymph node metastases were evident at the time of euthanasia. The histotype of the tumour, the coincidence with injections and the histological description make the hypothesis of an injection-site sarcoma likely. To the authors' knowledge, this is the first case of an injection-site sarcoma at the site of a cisplatin injection.