Cardiac myxoma in the pulmonary trunk of a canine: Presence of mesenchymal stem-like cells

Cardiac myxoma is a rare disease in dogs. Its histogenic origin has not yet been established, but the involvement of mesenchymal stem cells has been suggested in humans. Here we report an encapsulated and benign cardiac myxoma located at the entrance to the pulmonary trunk of the heart of an 8-year-old male Yorkshire Terrier dog presenting sudden death in the absence of clinical symptoms related to cardiac alterations. Hematoxylin/eosin staining demonstrated the mixoid origin of the myxoma, showing abundant hypocellular stroma with polygonal cells, while immunohistochemistry (IHC) corroborated its mesenchymal lineage with the detection of vimentin and α-SMA positive cell populations. In addition, IHC showed some cell populations in the stroma to be immunoreactive to the pluripotency markers Oct4 and ALDH1. In conclusion, this is the first report of the presence of mesenchymal stem-like cells with an Oct4 and ALDH1-positive IHC profile in a canine cardiac myxoma.