From the Guidelines
The fat anterior to the psoas muscle below the lower pole of the left kidney does contain lymph nodes that are part of the lymphatic chain for the kidneys and a potential location for metastatic lymph nodes from renal cell carcinoma. This area, known as the para-aortic region, is a common location for metastatic lymph nodes from renal cell carcinoma, as kidney cancers typically spread via lymphatic channels to regional lymph nodes, including those in the renal hilar, paracaval, para-aortic, and interaortocaval regions 1. The lymphatic drainage from the left kidney particularly involves nodes along the left renal vein, para-aortic nodes, and nodes anterior to the psoas muscle. During surgical management of kidney cancer, such as radical nephrectomy, lymph node dissection in these areas is often performed when there is clinical suspicion of nodal involvement, as recommended in the management of stage III RCC, where radical nephrectomy is recommended with lymph node dissection in those with clinical enlarged lymph nodes 1. Imaging studies like CT scans with contrast or MRI are used to evaluate these regions for enlarged lymph nodes that might indicate metastatic spread, and the presence of metastatic disease in these lymph nodes significantly impacts staging, prognosis, and treatment planning for patients with kidney cancer. Key considerations in the management of renal cell carcinoma include the stage of the disease, with treatments ranging from partial nephrectomy for stage I tumors to radical nephrectomy and systemic treatment for more advanced stages, and the importance of evaluating for metastatic disease, including in the lymph nodes anterior to the psoas muscle, to guide treatment decisions and improve patient outcomes 1.
From the Research
Lymph Nodes in the Psoas Muscle Region
- The psoas muscle is located in the retroperitoneal space, and the fat anterior to the psoas muscle can contain lymph nodes that are part of the lymphatic chain for the kidneys 2, 3.
- These lymph nodes can be a potential location for metastatic lymph nodes from renal cell carcinoma (kidney cancer) 2, 3, 4.
- The lymphatic drainage of the kidneys is unpredictable, and the newer available imaging techniques are still immature in detecting small lymph node metastases 3.
- Studies have shown that lymph node involvement in patients with RCC is evaluated with numerous modalities, including color Doppler sonography, magnetic resonance imaging (MRI), lymphotrophic nanoparticle enhanced MRI, multidetector-row computed tomography (MDCT), F-fluoro-2-deoxyglucose positron emission tomography (FDG-PET), and PET/CT 4.
Metastasis to the Psoas Muscle
- Skeletal muscle is a very rare location for the metastasis of renal cell carcinoma (RCC), and only one case of solitary metastasis to the psoas muscle has been reported 5.
- A case study reported a 63-year-old male patient with late recurrence (14 years) after left side radical nephrectomy for RCC, who presented with a solitary metastasis to the right psoas muscle 5.
- Another case study reported a 68-year-old male patient with non-Hodgkin lymphoma of the kidney, who presented with perinephric stranding and bulky psoas mimicking pyelonephritis 6.
Imaging and Diagnosis
- Imaging modalities such as CT and MRI can be used to evaluate the lymph node status in patients with RCC, but the current diameter criteria for determination of positive lymph nodes should be re-evaluated as micro-metastases are frequently overlooked 4.
- FDG-PET has the highest specificity for confirming lymph node involvement and extent of involvement, but due to its low sensitivity, clinicians should be skeptical of negative reports of lymph node involvement in RCC patients 4.
- A combination of MRI and FDG-PET may offer the highest accuracy for determining lymph node involvement in renal cancer 4.