What is the significance of a 3 mm nodule found in the fat anterior to the psoas muscle below the lower pole of the left kidney on 3-year imaging, initially reported as new but later determined to be present 1.5 months following partial nephrectomy for a 1.3 cm Chromophobe Renal Cell Carcinoma (RCC)?

From the Guidelines

The 3 mm nodule found anterior to the psoas muscle below the left kidney is likely not concerning for recurrent cancer, and continued surveillance with periodic imaging is recommended to monitor both the nodule and the kidney for any changes. This nodule was initially labeled as new but was actually present shortly after partial nephrectomy for chromophobe renal cell carcinoma. Given that the original tumor was small (1.3 cm), low stage (T1a), and a chromophobe subtype with no aggressive features, the risk of recurrence or metastasis is very low, as supported by the American College of Radiology guidelines 1. Chromophobe RCC generally has an excellent prognosis with over 90% survival at 10 years for T1a tumors. The small nodule is most likely post-surgical changes, scar tissue, or a benign lymph node rather than metastatic disease.

Key Considerations

• The nodule's presence shortly after surgery suggests it may be related to post-surgical changes rather than a new metastatic lesion.
• The patient's original tumor characteristics (small size, low stage, chromophobe subtype) indicate a low risk of recurrence or metastasis.
• Continued surveillance is crucial for early detection of any potential changes or recurrence, with guidelines suggesting periodic imaging (typically annual or biannual) for low-risk patients 1.
• The American College of Radiology guidelines recommend CT of the abdomen without and with IV contrast for surveillance after localized RCC ablation, which can help detect recurrences in the treatment bed and other common sites of metastases 1.

Recommendations

• Continue surveillance with periodic imaging (typically annual or biannual) to monitor both the nodule and the kidney for any changes.
• If symptoms like flank pain, blood in urine, or unexplained weight loss occur, contact the urologist promptly.
• No specific treatment is needed for this nodule at this time, just continued observation, as the risk of recurrence or metastasis is low, and the benefits of surveillance outweigh the risks of over-surveillance 1.

From the Research

Clinical Significance of a 3 mm Nodule

The clinical significance of a 3 mm nodule found in the fat anterior to the psoas muscle below the lower pole of the left kidney on 3-year imaging, initially reported as new but later determined to be present 1.5 months following partial nephrectomy for a 1.3 cm Chromophobe Renal Cell Carcinoma (RCC), can be considered in the context of the provided studies.

• The studies 2, 3, 4, 5, 6 focus on the characteristics, prognosis, and management of Chromophobe Renal Cell Carcinoma (ChRCC), but do not directly address the significance of a small nodule in the fat anterior to the psoas muscle.
• However, it is known that ChRCC generally has a favorable prognosis with a low tendency to progress and metastasize 4.
• The presence of a small nodule, particularly one that is stable over time, may not necessarily be indicative of metastatic disease or recurrence of ChRCC.
• Further evaluation, potentially including imaging characteristics and biopsy, would be necessary to determine the nature of the nodule.

Imaging Characteristics

• Studies have explored the use of CT features to differentiate between renal oncocytoma and chromophobe renal cell carcinoma 5.
• The location, tumor size, relative density ratio, segmental enhancement inversion (SEI), necrosis, and perirenal fascia thickening are among the CT imaging features that have been evaluated.
• However, the application of these features to the evaluation of a small nodule in the fat anterior to the psoas muscle is not directly addressed in the provided studies.

Prognosis and Management

• The prognosis for patients with ChRCC is generally favorable, with a low risk of tumor progression, metastasis, and cancer-specific death 4.
• Patient gender, clinical and pathological tumor stage, and sarcomatoid differentiation are significant predictors of recurrence-free survival (RFS) and cancer-specific survival (CSS) for ChRCC 4.
• The management of ChRCC often involves surgical resection, and the therapeutic approach may be extrapolated from clear cell RCC (ccRCC) treatments or studies that combine several forms of non-clear cell RCC subtypes 6.