Computed Tomographic Characteristics of Feline Renal Cell Carcinoma and Renal Lymphoma: A Comparative Analysis

This retrospective, multicenter study aimed to identify key computed tomography (CT) features that differentiate renal cell carcinoma (RCC) from lymphoma, the two most common feline renal neoplasms. CT images from 25 cats with renal tumors (15 RCC and 10 lymphoma) were evaluated. Of the RCC cases, 10 were diagnosed through histopathology and 5 through FNA. Among the lymphoma cases, two were extranodal lymphoma, including one case of primary renal lymphoma, and eight were gastrointestinal (GI) lymphoma with renal involvement. Qualitative features (tumor distribution, growth pattern, and enhancement characteristics) and quantitative parameters (tumor size and attenuation values) from triphasic or single post-contrast-enhanced CT scans were analyzed and compared. RCC typically presented as unilateral (93.3%) masses with expansile growth (73.3%) and heterogeneous enhancement among contrast-enhancing tumors (100%). Lymphoma more often showed bilateral involvement (60%), infiltrative growth (50%), and homogeneous enhancement (90%) (p < 0.001). Tumor vessel enhancement was observed exclusively in RCC. Compared with lymphoma, RCC demonstrated significantly higher attenuation values in the late nephrographic/early excretory phase. While histopathology remains the gold standard, this study provides a detailed CT analysis of these tumors, specifically within a feline population.