What is the nature of a 3mm nodule in the fat anterior to the psoas muscle, which appeared after partial nephrectomy (surgical removal of a portion of the kidney) for a 1.3 cm chromophobe renal cell carcinoma (RCC) and has remained stable over three years?

From the Research

The 3mm nodule in the fat anterior to the psoas muscle is most likely post-surgical scarring or fibrosis related to the partial nephrectomy performed. This conclusion is supported by several key observations: the nodule was not present before surgery but appeared after the procedure, and it has remained stable over three years without significant growth. The small size (3mm) and stable nature suggest a benign post-surgical change rather than recurrent renal cell carcinoma. The fact that it appeared shortly after surgery and has remained relatively unchanged for three years is reassuring, as seen in studies such as 1, which describes the CT and MR imaging findings after microwave ablation of clinical stage 1 renal cell carcinoma (RCC), where ablation zones decreased in size but did not resolve during surveillance, and local recurrence rates were higher for T1b compared to T1a. Post-surgical changes including small fibrotic nodules are common findings after partial nephrectomy and typically represent normal healing processes, as discussed in 2, which highlights the incidence and features of surgically resected benign nodules in lung cancer screening. The other finding of fat necrosis with chronic inflammation in the surgical bed further supports that these are expected post-surgical changes rather than disease recurrence, as seen in 1. Continued surveillance imaging is still appropriate to ensure the nodule remains stable, but its characteristics strongly suggest it is a benign post-surgical change rather than recurrent chromophobe renal cell carcinoma, in line with the principles outlined in 3 for the clinical staging and restaging of renal cell carcinoma. Key points to consider include:

• The nodule's small size and stable nature
• The appearance of the nodule after surgery and its lack of significant growth over three years
• The presence of post-surgical changes, such as fat necrosis and chronic inflammation, in the surgical bed
• The importance of continued surveillance imaging to monitor the nodule's stability.