From the Guidelines
This lesion most likely represents a benign process rather than a malignant one, given its small size, stability over time, and the fact that it was present shortly after partial nephrectomy. The patient's history of stage T1a low-grade Chromophobe Renal Cell Carcinoma (RCC) and the presence of a 3mm lesion anterior to the psoas, caudal to the lower pole of the left kidney, 1.5 months post-partial nephrectomy, suggests a low risk of malignancy. According to the American College of Radiology Appropriateness Criteria 1, for low-risk/T1 tumors, abdominal imaging is recommended, but the small size and stability of the lesion are reassuring features.
- The lesion's characteristics, such as its small size (3mm) and stability over time, are more consistent with a benign process, such as post-surgical changes, scarring, or a small benign nodule in the retroperitoneal fat.
- Malignant lesions, particularly metastases, typically demonstrate more substantial growth over a similar timeframe 1.
- The American Society of Clinical Oncology clinical practice guideline 1 suggests that small renal masses (SRMs) are often benign or indolent, and that imaging modalities cannot reliably discriminate between malignant and benign SRMs.
- Given the low risk of malignancy and the potential for benignity, continued surveillance imaging is still recommended to monitor this lesion, even though its characteristics strongly suggest it is benign 1.
- If there are concerns, a multidisciplinary discussion with urology and radiology might be beneficial to determine if any additional workup is necessary.
From the Research
Lesion Characteristics
- The lesion is 3mm in size and located anterior to the psoas, caudal to the lower pole of the left kidney.
- It has been present for 1.5 months post-partial nephrectomy for stage T1a low-grade Chromophobe Renal Cell Carcinoma (RCC).
Possible Causes
- The lesion could be a malignant process, potentially a recurrence of the Chromophobe Renal Cell Carcinoma 2, 3.
- It could also be a benign process, such as a cyst or a non-neoplastic lesion 4, 5.
Chromophobe Renal Cell Carcinoma
- Chromophobe Renal Cell Carcinoma is a rare subtype of renal cell carcinoma, accounting for 4-6% of renal cell carcinoma subtypes 2.
- It generally has a good prognosis, but can occasionally exhibit aggressive behavior, such as retrograde venous invasion and gain of chromosome 21 3.
- Immunohistochemical studies have shown that chromophobe renal cell carcinoma is positive for epithelial membrane antigen and E-cadherin, but negative for vimentin and N-cadherin 5.
Nephron-Sparing Surgery
- Nephron-sparing surgery (NSS) is a safe and effective method for treating carefully selected renal cell carcinoma patients, including those with chromophobe renal cell carcinoma 6.
- The study found that NSS can be performed with minimal complications and low recurrence rates, making it a viable option for patients with small renal tumors 6.