Squamous Cell Carcinoma of the Tongue in Captive Rhesus Monkeys ( Macaca mulatta )

Background Tongue squamous cell carcinoma (TSCC) is a typical and prevalent neoplasm in non‐human primates (NHPs). However, comprehensive pathological and immunohistochemical analyses of TSCC in rhesus monkeys have been infrequently documented. Methods Three rhesus monkeys with TSCC were sourced from the same breeding facility. Laboratory tests, gross observation of the lesion tissue, and human papillomavirus content testing using real‐time fluorescence PCR method of the animals were carried out. The animals underwent necropsy for examination of tissues and organs, followed by histopathological and immunohistochemical analysis. Results The clinical manifestations observed across all animals included salivation, swelling, sclerosis, and ulceration of the tongue. All three rhesus monkeys were euthanized due to deteriorating health conditions. No abnormalities were noted in other organs during post‐mortem examination except for their tongues. Histopathological examination revealed an invasive tumor characterized by nests of polygonal cells within the stroma, accompanied by significant desmoplastic reactions and occasional cancerous beads. All cases demonstrated positive immunolabeling for p63, CK5/6, p40, CK19, CK7, and CK20 via immunohistochemistry (IHC) analysis. Conclusions The clinical manifestations and pathological examination of the three cases were consistent with the characteristics of highly differentiated squamous cell carcinoma. Additionally, immunohistochemical analysis revealed positive expression of p63, CK5/6, p40, CK19, CK7, and CK20. In three cases, the results of human papillomavirus were negative. This study provides an important reference for the diagnosis of TSCC in rhesus monkeys.