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

## TL;DR

This study compares CT imaging features of two common kidney tumors in cats to help distinguish between them for better diagnosis and treatment.

## Contribution

The study identifies specific CT characteristics that differentiate feline renal cell carcinoma from lymphoma.

## Key findings

- RCC typically appears as unilateral, solitary masses with heterogeneous enhancement and visible tumor vessels.
- Lymphoma often shows bilateral involvement, multiple lesions, and homogeneous enhancement.
- RCC had significantly higher attenuation values in the late nephrographic/early excretory phase compared to lymphoma.

## Abstract

Kidney tumors in cats, though relatively uncommon, represent an important clinical entity in feline medicine. Among the various types, renal cell carcinoma (RCC) and lymphoma are the two most commonly diagnosed renal neoplasms. The goal was to identify key imaging features that distinguish these tumors. The study found that RCC usually appeared as a unilateral, solitary mass with heterogeneous enhancement and visible tumor vessels. In contrast, lymphoma commonly presents with bilateral involvement, multiple lesions, and homogeneous enhancement patterns. Quantitative analysis revealed that RCC exhibited significantly higher attenuation values in the late nephrographic/early excretory phase of contrast imaging compared to lymphoma. These findings are important because they improve early and accurate diagnosis, which can lead to better treatment decisions and improved care for cats with kidney tumors.

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.