Spontaneous neoplasms of the marmoset (Callithrix jacchus). Oral and nasopharyngeal squamous cell carcinomas.

Eight spontaneous highly invasive oral and nasopharyngeal squamous cell carcinomas were observed over an 18-month period in a breeding colony of the common marmoset (Callithrix jacchus). Affected marmosets were predominantly males over four years of age. The incidence of this tumor in the four-year-plus age group was 4.9%. The tumors were locally invasive through the palate to the nasal cavity, retrobulbar space and cranial cavity in some marmosets with lung metastases present in three cases.