Do Postvaccinal Sarcomas Occur in Australian Cats?

A soft tissue sarcoma occurred in the interscapular area of a cat, 1 to 7 months after vaccination at that site. The vaccine contained inactivated feline panleucopaenia virus combined with modified live feline herpesvirus and calicivirus. The tumour showed histological features of both fibrosarcoma and malignant fibrous histiocytoma. The tumour was observed to evolve from the site of a presumed postvaccinal granuloma. Local recurrence 6 weeks post excision necessitated more radical resection. Euthanasia was performed 2 years later when pleural effusion developed. The cause of effusion was not determined. There was no palpable evidence of local tumour regrowth at the time of euthanasia. A causal relationship between vaccination and sarcoma formation is considered based on the temporal association between the two events, the anatomical location of the tumour and histopathology consistent with postvaccinal sarcomas reported overseas. Six other vaccine site fibrosarcomas, potentially vaccine associated using the above criteria, are summarised.