A retrospective study (2019-2024) of neoplastic and non-neoplastic lesions in biopsy samples from exotic pet mammals in Hong Kong

This retrospective study analysed pathological findings in tissue biopsies from eight exotic pet mammal species submitted to the CityU Veterinary Diagnostic Laboratory in Hong Kong between January 2019 and December 2024. Tissue biopsies were submitted from 287 rabbits, 161 hamsters, 131 hedgehogs, 64 guinea pigs, 22 chinchillas, 20 rats, seven mice and six ferrets. Across all investigated species, both neoplastic and non-neoplastic lesions were prevalent with species-specific tendencies in affected organ system. Skin and soft tissues, along with the reproductive system, were the most affected organ system in all investigated species. Except for chinchillas, neoplastic lesions outnumbered non-neoplastic lesions in all studied species. Adenocarcinoma (15.2%) mostly of the uterus and mammary gland was the most commonly diagnosed lesion in rabbits followed by trichoblastoma (14.5%). Adenoma (14.6%), mostly of the mammary gland, was the most frequently submitted lesion from hamsters, followed by lymphoma (9.8%). Sarcomas of uncertain differentiation were the most prevalent lesions in hedgehogs (21.4%) and were primarily cutaneous and uterine sarcomas, while cystic endometrial hyperplasia (CEH) ranked second (15.3%). In guinea pigs, CEH (21.5%) was the most commonly identified pathology followed by mammary adenoma (13.8%). The reproductive system accounted for more than half of the lesions diagnosed in chinchillas with CEH and endometritis being the most prevalent lesions, each representing 18.2% of submitted biopsies from chinchillas. Mammary gland fibroadenoma was the most frequent diagnosis in rats (55%) and equal in frequency with adenocarcinoma in mice, each representing 25% of submitted biopsies. Ferrets had seven distinct diagnoses. These findings emphasize the significance of reproductive and integumentary health in exotic pet mammals and reveal species-specific disease patterns critical for diagnosis and preventive care.