Ganglioneuroma in a Meller's chameleon (Triocerosmelleri)

Nervous system neoplasia is rarely reported in reptiles, with most reports representing gliomas. A captive, 9-year-old Meller's chameleon (Trioceros melleri) was euthanized for weight loss and lethargy. At necropsy, a 2 cm-diameter mass was effacing the right adrenal gland and adhered to the kidney. The skin had two, 0.8-1.0 cm-diameter, firm, pale-yellow masses over the right leg and left shoulder. The fat bodies were small. Histologically, the adrenal gland and peri-adrenal soft tissues were effaced by an expansile, moderately cellular neoplasm entrapping remnant chromaffin and interrenal cells and invading the kidney. The neoplasm was composed of two cell populations resembling well-differentiated neurons and Schwann cell-like peripheral nerve sheath elements. Cellular atypia was minimal. The skin was multifocally elevated and expanded by invasive, unencapsulated neoplasms composed of intersecting streams of neoplastic spindle cells with abundant eosinophilic, finely vacuolated cytoplasm, oval nuclei, marked anisocytosis and anisokaryosis, and occasional mitoses; these were interpreted as sarcomas. The fat bodies had marked atrophy. Immunohistochemistry was non-contributory (glial fibrillary acidic protein, neuron-specific enolase, synaptophysin, NeuN, chromogranin, S100 and vimentin) or negative (AE1/AE3) in neoplastic cells. The adrenal gland mass was diagnosed as a ganglioneuroma, which is a neoplasm of the peripheral nervous system originating from the sympathetic ganglia of the autotomic nervous system. Ganglioneuroma is rarely reported in veterinary species, and this is the first report in a reptile. The origin of this ganglioneuroma was likely neural crest cells of the adrenal gland. It is unknown whether the dermal masses were related to the ganglioneuroma or were unrelated sarcomas.