From the Guidelines
The 3mm nodule in the fat anterior/lateral to the psoas muscle is likely a benign finding that does not require immediate intervention, given its stability over three years and the patient's history of completely resected chromophobe renal cell carcinoma. This assessment is based on the latest guidelines from the European Association of Urology, which emphasize the importance of individualized treatment decisions and the role of surveillance in managing small renal masses 1. The patient's history of partial nephrectomy for a 1.3cm exophytic chromophobe renal cell carcinoma, a type of cancer with limited metastatic potential, as noted in the American Society of Clinical Oncology clinical practice guideline 1, further supports a conservative approach. Key points to consider include:
- The nodule's small size and stability over time, which suggest a low risk of malignancy
- The patient's history of completely resected chromophobe renal cell carcinoma, which reduces the likelihood of recurrent cancer
- The importance of continued surveillance imaging to monitor the nodule's size and characteristics, as recommended by the European Association of Urology guidelines 1
- The potential for post-surgical changes to mimic recurrent cancer, highlighting the need for careful evaluation and monitoring. Given these considerations, continued surveillance imaging every 12 months for at least 5 years post-surgery is recommended to ensure the nodule remains stable, with further evaluation or biopsy considered only if changes are detected 1.
From the Research
Clinical Significance of a 3mm Nodule
- The provided studies do not directly address the clinical significance of a 3mm nodule in the fat anterior/lateral to the psoas muscle, in a patient with a history of partial nephrectomy for a 1.3cm exophytic chromophobe renal cell carcinoma (RCC) 2, 3, 4, 5, 6.
- However, study 3 mentions that smaller nodules are more likely to be benign, and the probability of malignancy is less than 1% for all nodules smaller than 6 mm.
- Study 6 recommends a follow-up CT at 12 months for nodules <4mm in high-risk persons, whilst for low-risk persons no follow-up is needed.
Nodule Growth and Malignancy
- Study 2 found that malignant nodules manifest growth slowly on follow-up CT, and 3-month follow-up CT has very low yield.
- Study 3 states that a malignant nodule that is entirely ground glass in appearance is typically slow growing.
- Study 4 found that perinephric myxoid pseudotumor of fat (PMPF) may show a median growth of 15% over 12 months.
Diagnostic Challenges
- Study 5 found that computed tomography (CT) does not seem to reliably predict perinephric fat invasion, but perinephric soft-tissue stranding was shown to be a significant factor for predicting perinephric fat invasion.
- Study 6 recommends a 10-step approach for evaluating sub-centimeter non-calcified pulmonary nodules, including assessment of nodule size, consistency, margin, and shape, as well as localization, nodule number, and presence or absence of growth.