What is the clinical significance of a 3 mm nodule located in the fat anterior to the psoas muscle, which was not present before partial nephrectomy for a 1.3 cm chromophobe renal cell carcinoma (RCC) but appeared one month post-operatively and has remained stable over three years?

From the Guidelines

The 3 mm nodule located in the fat anterior to the psoas muscle is likely a post-surgical change rather than recurrent cancer, and given its stability over three years, continued surveillance rather than intervention is appropriate. The nodule's appearance shortly after partial nephrectomy and its stable nature over three years suggest it is more likely related to the surgical procedure than to disease recurrence. The location of the nodule in an area that was surgically manipulated also supports this interpretation. According to the most recent guidelines, for low-risk/T1 tumors, such as the 1.3 cm chromophobe renal cell carcinoma (RCC) in this case, the recommended follow-up includes chest imaging every 12 to 24 months for 3 to 5 years and abdominal imaging, with some guidelines suggesting a baseline study between 3 and 12 months after partial nephrectomy, then yearly for 3 to 5 years 1. Given the low risk of recurrence for T1a chromophobe RCC and the stable nature of the nodule, the current approach aligns with standard surveillance recommendations. The fact that most recurrences occur within 3 years after treatment, with a median time to relapse of 1 to 2 years, and the nodule has remained stable beyond this period, further supports the decision for continued surveillance rather than immediate intervention 1. Key points to consider in the management of this patient include:

• The nodule's small size and stable nature over three years
• The location of the nodule in an area surgically manipulated during partial nephrectomy
• The low risk of recurrence for T1a chromophobe RCC
• Adherence to standard surveillance imaging guidelines for low-risk RCC, as outlined in the most recent recommendations 1.

From the Research

Clinical Significance of a 3 mm Nodule

The clinical significance of a 3 mm nodule located in the fat anterior to the psoas muscle, which appeared one month post-operatively after partial nephrectomy for a 1.3 cm chromophobe renal cell carcinoma (RCC) and has remained stable over three years, can be assessed based on the available evidence.

Imaging Features and Diagnosis

• The study by 2 highlights the importance of ultrasonography (US) and fine needle aspiration biopsy in diagnosing metastatic recurrence along the surgical scar.
• The study by 3 emphasizes the need for careful attention to imaging technique and the use of unenhanced and contrast-enhanced CT or magnetic resonance imaging (MRI) to accurately characterize indeterminate renal lesions.
• The study by 4 compares the sensitivity and specificity of contrast-enhanced ultrasound (CEUS), computed tomography (CT), and magnetic resonance imaging (MRI) in evaluating unclear renal lesions, and finds that CEUS shows a comparable sensitivity, specificity, positive predictive value, and negative predictive value to CT and MRI.

Management and Follow-up

• The study by 5 discusses the clinical need for improved tools to aid in the pretreatment characterization of renal tumors, and highlights the potential of novel imaging tools such as multiparametric magnetic resonance imaging, molecular imaging, and radiomics.
• The study by 6 provides guidance on the investigation, differential diagnosis, and follow-up of nodules in the liver, and emphasizes the importance of considering any nodule in a cirrhotic liver as hepatocellular carcinoma until otherwise proven.

Relevance to the Present Case

• The nodule in question is located in the fat anterior to the psoas muscle, which is not a typical location for a metastatic lesion from a renal cell carcinoma.
• The stability of the nodule over three years suggests that it may be a benign lesion, such as a fibrous nodule or a granuloma.
• However, the appearance of the nodule one month post-operatively after partial nephrectomy for a chromophobe renal cell carcinoma raises the possibility of a metastatic lesion, and further evaluation and follow-up may be necessary to determine the nature of the nodule.