Granular cell tumour in an endangered Puerto Rican Amazon parrot (Amazon vittata)

A 3 cm diameter mass from the metacarpus of a Puerto Rican Amazon parrot wa s diagnosed as a granular cell tumour based on light microscopy. The cytopl asmic granules were periodic-acid Schiff positive and diastase resistant. U ltrastructural characteristics of the cells included convoluted nuclei and the presence of numerous cytoplasmic tertiary lysosomes. This is only the s econd granular cell tumour reported in a bird. We speculate that most granu lar cell tumours are derived from cells that are engaged in some type of ce llular degradative process, creating a similar morphologic appearance, but lacking a uniform histogenesis.