What is the significance of a persistent 3 mm nodule anterior to the psoas muscle, adjacent to the left kidney, after partial nephrectomy for Chromophobe renal cell carcinoma (RCC)?

From the Guidelines

The 3 mm nodule found anterior to the psoas muscle, adjacent to the left kidney, after partial nephrectomy for Chromophobe renal cell carcinoma (RCC) is likely a post-surgical change rather than a recurrence of the cancer, and continued surveillance imaging is recommended to ensure the nodule remains stable or decreases in size over time. This assessment is based on the small size of the nodule, its stable appearance, and the fact that the original cancer was a low-grade T1a chromophobe RCC without aggressive features. According to the most recent guidelines, such as those outlined in the American College of Radiology (ACR) Appropriateness Criteria for post-treatment follow-up and active surveillance of clinically localized renal cell carcinoma 1, CT of the abdomen is the most commonly used method for imaging surveillance after localized RCC ablation. The guidelines suggest that a lack of contrast enhancement is considered the hallmark of successful treatment, but many completely ablated lesions show enhancement in the immediate post-treatment period, which may persist for several weeks to months.

Key considerations in evaluating this nodule include:

• The nodule's small size (3 mm) and stable appearance over time, which are favorable factors suggesting a benign nature.
• The technical factors influencing the visibility of the nodule across different imaging studies, such as slice thickness and image resolution, as discussed in the ACR guidelines 1.
• The importance of continued surveillance to monitor for any changes in the nodule's size or characteristics, as recommended by the guidelines for post-treatment follow-up of RCC patients 1.

Given the information provided and the current guidelines, the most appropriate course of action is to continue surveillance imaging, preferably with CT of the abdomen, to monitor the nodule's stability or regression over time, as this approach balances the need for vigilance against the risk of recurrence with the potential risks and burdens of over-surveillance, in line with recommendations from studies such as 1 and 1.

From the Research

Significance of a Persistent 3 mm Nodule

The significance of a persistent 3 mm nodule anterior to the psoas muscle, adjacent to the left kidney, after partial nephrectomy for Chromophobe renal cell carcinoma (RCC) can be understood by considering the following points:

• Chromophobe RCC is a distinct subtype of renal cell carcinoma with a generally favorable clinical course 2, 3.
• The presence of a nodule near the site of partial nephrectomy could indicate residual disease or recurrence, although the small size of the nodule (3 mm) may suggest a benign lesion or a non-significant finding.
• Studies have shown that Chromophobe RCC has a low malignant potential, with reported 5-year and 10-year survival rates of 78% to 100% and 80% to 90%, respectively 4.
• However, a subset of patients with Chromophobe RCC may progress, and factors such as tumor size, pT stage, microscopic necrosis, and sarcomatoid change have been identified as predictors of aggressive disease 4, 5.

Clinicopathologic Features

The clinicopathologic features of Chromophobe RCC that may be relevant to the significance of the persistent nodule include:

• Tumor size: larger tumors are associated with a higher risk of aggressive disease 4, 5.
• pT stage: higher pT stages are associated with a higher risk of aggressive disease 4, 5.
• Microscopic necrosis: presence of necrosis is associated with a higher risk of aggressive disease 4, 5.
• Sarcomatoid change: presence of sarcomatoid features is associated with a higher risk of aggressive disease 4, 5.

Diagnostic Considerations

The diagnostic considerations for a persistent nodule near the site of partial nephrectomy for Chromophobe RCC include:

• Residual disease or recurrence: the nodule could represent residual disease or recurrence of the primary tumor.
• Benign lesions: the nodule could represent a benign lesion, such as a cyst or a hematoma.
• Other malignancies: the nodule could represent a separate malignancy, such as a metastasis from another primary tumor.
• Imaging characteristics: the imaging characteristics of the nodule, such as its size, shape, and enhancement pattern, can help guide the diagnosis 6.