A five-year-old female red deer (Cervus elaphus) was in poor condition and severely lame on the left hindleg owing to a 19.4 cm x 15.9 cm mass involving and destroying the distal end (head) of metatarsal bones III and IV, the proximal sesamoid bones and the first phalanges (III and IV). The histopathological analysis revealed a spindle cell tumour with frequent palisade arrangement (Antoni type A pattern), and with highly anaplastic tumour cells in some areas. Structures resembling peripheral nerves were identified within the tumour. The neoplastic cells reacted with vimentin in a cytoplasmic pattern, and almost all of them reacted with S-100 protein in a nuclear and cytoplasmic pattern and did not express neurofilament, glial fibrillary acidic protein or keratins. This immunophenotype and the histopathological features were consistent with a diagnostic of malignant schwannoma. It was atypical because of the species affected, the location and the local malignancy.
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