Abstract
Background:
Renal cell carcinoma (RCC) is common cancer derived from the renal epithelium. One of the rarest cases of RCC is sarcomatoid RCC (sRCC). The occurrence of sRCC in animals is not clearly demonstrated.
Aim:
This study aimed to observe the clinicopathological characteristics of sRCC in animals from East Java, Indonesia, from 2017 to 2022.
Methods:
This study used patients which were histopathologically diagnosed with sRCC in our laboratory from 2017 to 2022. The data of clinical characteristics of animals, hematology, serology, histopathology, and immunohistochemistry were retrieved and tabulated. The data was qualitatively and quantitatively analyzed using a simple descriptive method and SPSS version 26, respectively.
Results:
Fourteen cases of sRCC in animals have been identified in this study. It was found in rodents, dogs, and cats. sRCC predominantly occurred in rodents (57.14%) without specific clinical signs. The common histopathological findings of sRCC were epithelial renal cells transition into elongated atypical spindle cells. In addition, other histopathological patterns of a renal epithelial cell such as clear cell, tubule-cystic, and papillary also have been found. Immunohistochemistry by using antibodies demonstrates that PAX8 is expressed on sRCC tissue samples 92.85% (13/14 samples). Hence, PAX8 could be used as a supporting method for establishing the diagnosis of sRCC in animals. Hematology and serological tests did not correlate to type of sRCC either pure sRCC or dedifferentiated sRCC. sRCC result in hypercreatinemia in rodents and dogs.
Conclusions:
This study shows that the incidence of sRCC in animals is rare. Animals with sRCC did not show any specific clinical signs. The histopathological finding is quite difficult to be differentiated from the other RCC. PAX8 expression on renal tissue samples is useful in supporting the diagnosis of sRCC in animals.

Key words: Animal, Kidney, PAX8, Renal cell carcinoma, Sarcomatoid