Clinical and Morphological Characteristics of Mastocytoma in Pet Rats
Authors: Bezviselnaya E. A. , Turitcyna E. G. 
Published: March 2024

Introduction. Mastocytoma is a tumour caused by the pathological proliferation of the population of the polymorphic mast cells (mastocytes) in the skin and/or visceral organs of vertebrates. Mastocytoma prevalence in pet rodents, rats in particular, as well as the clinical and morphological characteristics of this neoplasia are currently almost unstudied, although these issues are of interest to the rodentologists in their practical work in diagnosing, choosing disease treatment strategy and predicting an outcome of an oncological disease. The aim of this work is to investigate the clinical and morphological characteristics of mastocytomas in pet rats.

Materials and Methods. The study was conducted in 2022–2023 at the site of the histological laboratory of the Applied Biotechnology and Veterinary Medicine Institute of Krasnoyarsk State Agrarian University. The objects of the study were the pet rats with the oncological diseases owned by the individuals in Krasnoyarsk and the Krasnoyarsk Krai. The research material was the biopsy samples obtained during the surgical treatment of tumours in living animals or collected during the pathoanatomical autopsy of the fallen ones. The comprehensive research was conducted using the clinical, pathoanatomical, histological and histochemical methods. The histological sections were stained with the hematoxylin and eosin to detect the connective tissue using the Van Gieson method, metachromasia of mast cells was detected with the toluidine blue.

Results. During the study of 164 cases of spontaneously developing neoplasia in pet rats, it was found that mastocytoma accounted for 6.7%. In the organs and tissues that had no visible pathological changes of inflammatory or neoplastic nature, the largest locations of mastocytes were recorded in the cutaneous integuments, in the stroma of mammary, salivary, clitoral and preputial glands, and subcutaneous lymph nodes. The mast cell infiltration was found in the stroma of the neoplasms of different genesis. Mastocytomas represented the solitary encapsulated nodules without signs of metastasis, including at the late stages of the pathological process. The low differentiated mammary gland mastocytoma was recorded in females and was not found in males. The cutaneous mastocytoma was a highly differentiated tumour and was found mainly in males. The high and moderate differentiated mastocytoma located in the hypoderm and having a favourable long-term prognosis was found in both sexes.

Discussion and Conclusion. The study of the clinical and morphological characteristics of the spontaneously developing mastocytoma in pet rats has revealed that mastocytoma as an independent nosological form is rare in these animals and has its distinctive features in females and males. The influence of age-related factors on the tumour incidence has not been revealed. The morphological characteristics of mastocytomas in rats are close to the types classified for dogs. The role of mastocytes in development of the oncological pathologies of various genesis in pet rats needs further research.