Avian Pathol: Retrobulbar rhabdomyosarcoma in a budgerigar (Melopsittacus undulatus).

This report describes a retrobulbar rhabdomyosarcoma in a 7-year-old male budgerigar (Melopsittacus undulatus). The bird was presented with orbital distension and exophthalmia of the left eye. The bird died during surgery. Necropsy revealed a tan-grey retrobulbar mass compressing all components of the left eye. Histopathologic examination showed that the mass was composed of sheets of spindle-shaped cells with pleomorphic nuclei, numerous mitotic figures, mononucleated or multinucleated giant cells, and typical strap cells. Neoplastic cells had no cross-striations in sections stained by phosphotungstic acid hematoxylin. The tumor cells did not invade surrounding tissues, including the retina, and there was no metastasis to other organs. Immunohistochemically, tumor cells were positive for desmin, vimentin, and alpha-smooth muscle actin, but were negative for S-100 protein and pancytokeratin.

2005;34:486-488.