2012 Volume 65 Issue 12 Pages 933-936
A 20-year-old female macaroni penguin (Eudyptes chrysolophus) with a large black mass of the beak was examined pathologically. At necropsy, the mass was solid, irregular and black color, and had invaded the upper jaw and the oral cavity. Metastasis of the tumor to the thoracic subcutaneous tissue was also observed. Histopathologically, epithelioid or spindle tumor cells with many intracytoplasmic black pigments and eosinophilic abundant cytoplasm showed a solid, invasive proliferation pattern. Tumor cells were positive for S-100 and PCNA and negative for Desmin and Pan-cytokeratin by an immunohistochemical analysis. Electron microscopically, intracytoplasmic melanin granules and melanosomes were observed. Based on these findings, the lesion is diagnosed as a malignant melanoma of the beak in a macaroni penguin.
