From the Guidelines
The post-partial nephrectomy soft tissue mass and the stable 3 mm nodule in the fat anterior to the psoas muscle are likely benign and not concerning for cancer recurrence, and therefore, continued routine surveillance is recommended rather than any immediate intervention. The soft tissue mass, given its location and characteristics, could be consistent with expected post-surgical changes such as fat necrosis, which is a common finding after partial nephrectomy 1. The small and stable nature of the 3 mm nodule anterior to the psoas muscle suggests it is likely a post-surgical change rather than recurrent cancer, as the growth rate of renal tumors is typically low, with a mean of 3 mm/year, and progression to metastatic disease is rare, reported in 1%-2% of patients 1.
Given the excellent prognosis of chromophobe renal cell carcinoma (RCC), especially at the T1A stage, with a low risk of recurrence, and considering the initial tumor was small with no aggressive features, the current evidence supports the notion that these findings are benign post-surgical changes rather than disease recurrence 1. The American College of Radiology Appropriateness Criteria and other guidelines emphasize the importance of imaging in the evaluation of patients with suspected soft-tissue masses, but also highlight the need for careful consideration of the clinical context and the potential for post-surgical changes to mimic recurrence 1.
Therefore, regular follow-up imaging should continue as scheduled to monitor both findings, but the current evidence does not support the need for immediate intervention or a change in the current surveillance plan 1. It is essential to weigh the risks and benefits of further diagnostic procedures or interventions, considering the patient's overall health, the natural history of the disease, and the potential impact on quality of life 1.
From the Research
Significance of Post-Partial Nephrectomy Soft Tissue Mass
- A post-partial nephrectomy soft tissue mass can be a concern for potential recurrence of renal cell carcinoma (RCC) 2.
- The risk of recurrence after nephrectomy is generally related to tumor stage, tumor grade, and patient performance status 2.
- Surveillance protocols are essential to detect potential recurrences, and the University of California Integrated Staging System (UISS) can categorize patients into different risk groups 2.
Stable 3 mm Nodule in the Fat Anterior to the Psoas Muscle
- A small nodule, such as a 3 mm nodule, may not be significant, especially if it is stable 3, 4.
- Small renal masses (≤ cT1a, less than 4 cm) have low malignant and metastatic potential, and 30% of small renal masses removed surgically are benign 3.
- Imaging characterization of renal masses, including small nodules, depends on whether the lesion is cystic or solid, and the Bosniak classification can be used for cystic lesions 5.
Diagnostic Approach
- Imaging techniques, such as CT-scan and MRI, are essential for the characterization of renal masses 4, 5.
- Renal percutaneous biopsy can be helpful in selected cases, especially for bilateral tumors or when a renal metastasis is suspected 4.
- Needle biopsy and open incisional biopsy are effective methods to histologically identify the nature of a soft-tissue mass 6.