Odontogenic myxoma of the mandible in a filly.

This research presents a case study of a rare form of odontogenic tumor called myxoma, detected in the mandible or lower jaw of a young horse. This tumor, which usually occurs infrequently in domestic animals, shows distinctive characteristics when observed under various forms of microscope studies.

Case Background

• The case under study was of a 1.5-year-old filly, taken to the Veterinary Medicine Teaching Hospital, University of Florida, for a significant swelling on the left side of the lower jaw, excess salivation, and an inability to consume food or liquid. An unpleasant smelling mass was found on physical examination, and x-ray examination pointed to the misalignment of the lower jaw and an irregular area of varied density.
• Due to the unfavorable prognosis and financial reasons, the filly was put down, and the only abnormality discovered during post-mortem was a glossy, lumpy, tan and off-white mass extending into the oral cavity, which had completely replaced two premolar teeth.

Testing and Findings

• Samples acquired during the post-mortem were subjected to various tests including Hematoxylin and Eosin staining, histochemical staining, and immunochemical staining, to investigate the presence and characteristics of different components like cytokeratin, vimentin, S-100 protein, lysozyme, and actin.
• The observations were made under a transmission electron microscope. The neoplasm, which was comprised of star-shaped and spindle cells haphazardly dispersed in a great amount of myxoid matrix, showed signs of extensive invasion and replacement of the mandibular bone.
• Immunochemically, the neoplastic cells were positive for vimentin, S-100, and lysozyme, but negative for cytokeratin and actin. On ultrastructural examination, it revealed widely spaced spindle-shaped cells encircled by amorphous material.

Conclusions

• The study provides a detailed characterization of odontogenic myxoma in a domestic animal. The rarity of this type of tumor in such animals makes this case particularly informative for future diagnosis and research in Veterinary Medicine.
• The variety of microscopy methods used offer a comprehensive understanding of the tumor’s microscopic and ultrastructural properties, which could benefit both veterinary pathologists and clinical veterinarians dealing with similar cases.