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 imaging 3 years after a partial nephrectomy for a 1.3 cm exophytic Chromophobe renal cell carcinoma (RCC)?

From the Guidelines

The 3 mm nodule found anterior to the psoas muscle below the left kidney is likely benign and represents either a small lymph node or residual post-surgical change rather than recurrent cancer. Given the patient's history of partial nephrectomy for a 1.3 cm exophytic Chromophobe renal cell carcinoma (RCC) with clear margins and favorable characteristics, the prognosis is excellent 1. The standard follow-up protocol for T1a chromophobe RCC typically involves imaging every 12 months for the first 3-5 years, and this nodule's stability since surgery suggests it is not concerning 1.

Key Considerations

• The nodule's small size (3 mm) and location anterior to the psoas muscle below the left kidney are not typical for recurrent RCC, especially given the primary tumor's small size (1.3 cm) and low stage (T1a) 1.
• The lack of contrast enhancement or significant growth over time, as would be expected in recurrent disease, further supports a benign nature 1.
• Continued routine surveillance imaging is appropriate, rather than immediate intervention, to monitor for any changes in the nodule or development of new symptoms 1.

Recommendations

• Continue with the standard follow-up protocol for T1a chromophobe RCC, with imaging every 12 months for the first 3-5 years 1.
• If new symptoms such as flank pain, blood in urine, or unexplained weight loss occur, contact the urologist promptly for evaluation 1.
• Given the current evidence and guidelines, there is no indication for immediate biopsy or intervention for this small, stable nodule 1.

From the Research

Nodule Significance

The provided studies primarily focus on pulmonary nodules, which may not be directly relevant to a 3 mm nodule found in the fat anterior to the psoas muscle, below the lower pole of the left kidney. However, some general information about nodules can be applied:

• Nodules are commonly identified on imaging studies, with approximately 1.6 million patients per year in the US having pulmonary nodules detected 2.
• The majority of nodules are benign, with at least 95% of all pulmonary nodules identified being benign 2.
• The probability of malignancy is less than 1% for all nodules smaller than 6 mm and 1% to 2% for nodules 6 mm to 8 mm 2.

Nodule Management

The management of nodules depends on their size, location, and patient risk factors:

• Small nodules (<6 mm) are more likely to be benign and can be followed with repeat imaging 2, 3.
• Larger nodules (≥8 mm) have a higher risk of malignancy and may require further evaluation, such as biopsy or surgical resection 2, 4.
• The Fleischner Society provides recommendations for measuring pulmonary nodules at CT, including technical requirements for accurate nodule measurement and directions on how to report nodule size and changes in size 5.

Extrapolation to the Given Scenario

While the provided studies focus on pulmonary nodules, the general principles of nodule management can be applied to other types of nodules:

• A 3 mm nodule found in the fat anterior to the psoas muscle, below the lower pole of the left kidney, is likely to be benign, given its small size.
• However, the patient's history of a partial nephrectomy for a 1.3 cm exophytic Chromophobe renal cell carcinoma (RCC) may increase the risk of malignancy, and further evaluation may be necessary.
• The management of this nodule would depend on various factors, including the patient's overall health, the presence of any symptoms, and the results of any additional imaging or diagnostic tests.

Key Points

• The majority of nodules are benign, but the risk of malignancy increases with nodule size.
• Nodule management depends on size, location, and patient risk factors.
• Further evaluation may be necessary for a 3 mm nodule in a patient with a history of RCC, despite its small size.