Squamous cell carcinoma of the oral cavity in an infant cynomolgus monkey

Squamous cell carcinoma was observed in the oral cavity in a one-year-old m ale cynomolgus monkey. Histopathologically, the tumor consisted of various shaped cells and ifs assemblies infiltrated into the surrounding connective tissues. Although no obvious metaplastic keratinized cancer pearls were fo und in the tumor cells, the intercellular bridges were observed. Immunohist ochemically, tumor cells were stained with anti-keratin, but not with anti- vimentin. On virological examinations, no papilloma virus antigen or Epstei n-Barr Virus small mRNA could not be detected. Under the electron microscop e, incomplete tonofibrils and desmosomes in the cytoplasm and microvillus o f the cell membrane were observed, suggesting a malignancy or low different iation of the tumor cells in the present case. This is the first case of sq uamous cell carcinoma observed in very young macaques, to our knowledge.