Malignant Rhabdoid Tumor in the Gastric Wall of an Aged Orangutan (Pongo pygmaeus)

A 34-year-old female orangutan ( Pongo pygmaeus) developed renal failure and became uremic. At necropsy, large gastric masses were present around the cardia and in the corpus. Abdominal metastases occurred in the liver, pancreas, and right ovary. Light microscopic examination of the tumor revealed polygonal cells with vesicular nuclei and prominent nucleoli. The growth pattern was predominantly solid. Focal areas contained excentric cytoplasmic intermediate filament inclusions, as identified by immunohistochemistry and electron microscopy. Immunohisiochemical procedures demonstrated mainly the vimentin type of intermediate filaments. Except for occasional cytokeratin, other intermediate fil…