Malignant Perivascular Epithelioid Cell Tumour in a Savannah Monitor (Varanus exanthematicus).

A 9-year-old male captive savannah monitor (Varanus exanthematicus) with a history of general debility was submitted for necropsy. Grossly, there were multiple white masses in the colon, mesorchium and tracheal adventitia. Histologically, the lesions were composed of epithelioid to spindloid neoplastic cells arranged in sheets to interlacing and interwoven bundles, and separated by abundant myxoid material or extensive stromal hyalinization and fibrosis with occasional chondroid metaplasia. Perivascular infiltration of epithelioid neoplastic cells was occasionally seen. Neoplastic cells were immunopositive for alpha-smooth muscle actin, melan-A and S100. The unique histological features and concurrent myogenic and melanocytic immunophenotypes suggest a malignant perivascular epithelioid cell tumour. To our knowledge, this is the first report of perivascular epithelioid cell tumours in a non-human species.