What is the significance of a 3 mm nodule in the fat anterior to the psoas muscle, present since one month post-partial nephrectomy for chromophobe RCC?

From the Guidelines

The 3 mm nodule in the fat anterior to the psoas muscle is likely a post-surgical change and not a concerning new finding, given its small size and presence since one month post-partial nephrectomy for chromophobe RCC, and therefore, no immediate intervention is needed. The nodule's stability and small size are key factors in this assessment, as it is common for post-surgical changes to occur in the operative field and surrounding tissues as part of the normal healing process 1. According to the ACR Appropriateness Criteria for post-treatment follow-up and active surveillance of clinically localized renal cell carcinoma, CT of the abdomen is the most commonly used method for imaging surveillance after localized RCC ablation, and it can detect recurrences in the treatment bed and other common sites of metastases in the abdomen 1. However, the lack of contrast enhancement or the development of new areas of enhancement in the treatment zone or new satellite or port site soft-tissue nodules should raise concern for residual or recurrent disease, and in these circumstances, a biopsy could be considered to identify the presence of viable neoplasm 1. In this case, given the nodule's small size and stability since the immediate post-operative period, continued surveillance imaging as part of the regular follow-up plan for the treated chromophobe RCC is appropriate, rather than immediate intervention or biopsy. Some key points to consider in the follow-up of this patient include:

• The use of CT of the abdomen with and without IV contrast to monitor for recurrences or metastases 1
• The evaluation of contrast enhancement of the treated lesions, which can be assisted by material decomposition techniques and iodine-only image data sets in dual-energy CT 1
• The consideration of biopsy if there is concern for residual or recurrent disease, based on the lack of spontaneous decline in enhancement or the development of new areas of enhancement 1.

From the Research

Significance of a 3 mm Nodule

• The provided studies do not directly address the significance of a 3 mm nodule in the fat anterior to the psoas muscle, present since one month post-partial nephrectomy for chromophobe RCC.
• However, study 2 discusses the use of imaging tests such as ultrasound, CT, MRI, and PET-CT for staging and re-staging of adults with cutaneous melanoma, which may be relevant to understanding the diagnostic approach for nodules in general.
• Study 3 investigates the impact of PET/CT and brain MRI for metastasis detection among patients with clinical T1-category lung cancer, but does not specifically address the significance of a 3 mm nodule in the context of chromophobe RCC.

Diagnostic Approach

• The diagnostic approach for a 3 mm nodule would likely involve imaging tests such as CT or MRI to characterize the nodule and determine its potential significance 2.
• Study 4 discusses the radiological diagnosis of pulmonary metastases, which may be relevant to understanding the diagnostic approach for nodules in the lung, but does not directly address the significance of a 3 mm nodule in the fat anterior to the psoas muscle.
• Study 5 investigates the clinical and diagnostic features of angiosarcoma with pulmonary metastases, which may be relevant to understanding the diagnostic approach for nodules in the lung, but does not directly address the significance of a 3 mm nodule in the context of chromophobe RCC.

Limitations

• The provided studies do not directly address the significance of a 3 mm nodule in the fat anterior to the psoas muscle, present since one month post-partial nephrectomy for chromophobe RCC.
• Therefore, it is not possible to draw conclusions about the significance of this nodule based on the provided evidence 6, 2, 3.