Metastatic squamous cell carcinoma with skeletal and spinal cord invasion in an African grey parrot (Psittacus erithacus)

Background Squamous cell carcinoma is a commonly reported neoplasm in avian species. Often locally invasive, it rarely distantly metastasizes. Superficial chronic ulcerative dermatitis (SCUD) is a commonly observed dermatologic condition in companion psittacine birds. Case description This report describes a case of metastatic squamous cell carcinoma in an African gray parrot (Psittacus erithacus) caused by malignant transformation of an initial SCUD lesion that developed over a 2.5-year period. The right humerus was previously amputated to treat a squamous cell carcinoma, but it recurred in the skin 4 months prior to presentation. The bird presented on referral with pelvic limb paresis, and computed tomography showed a large, more right sided, paraspinal mass involving the right caudal coelom and effacing the lungs, ribs, and vertebral canal, resulting in the presenting neurologic signs. The patient was euthanized, and limited necropsy diagnosed the coelomic mass as a squamous cell carcinoma effacing the liver. Conclusions Though uncommonly reported, squamous cell carcinoma may distantly metastasize to other parts of the body even with partial or seemingly complete excision. SCUD is still a poorly understood condition and should be further researched to determine etiology and find more effective therapies. Case relevance This is the first report of a metastatic squamous cell carcinoma invading the vertebral canal and spinal cord resulting in upper motor neuron signs in the pelvic limbs. Chronic inflammation may lead to malignant transformation, and once squamous cell carcinoma has developed, the goal of therapy should be complete surgical excision where possible.