Is the fat anterior to the psoas muscle, below the lower pole of the kidney, which is part of the perirenal (perirenal) fat, an uncommon location for lymph node metastasis in kidney cancer?

From the Guidelines

The fat anterior to the psoas muscle below the lower pole of the kidney is an uncommon location for lymph node metastasis in kidney cancer. This is because kidney cancer (renal cell carcinoma) typically metastasizes to regional lymph nodes in the renal hilum, paracaval, para-aortic, and interaortocaval regions, as stated in the NCCN Guidelines for Kidney Cancer 1. The perirenal fat is the fatty tissue immediately surrounding the kidney within Gerota's fascia, while the fat anterior to the psoas muscle below the kidney's lower pole is outside this fascial envelope. Lymphatic drainage from the kidney primarily follows the renal vein pathway toward the central retroperitoneal lymph nodes rather than inferiorly toward the psoas region. When kidney cancer does metastasize to lymph nodes, it most commonly affects those along the renal vessels, the paracaval nodes for right-sided tumors, and para-aortic nodes for left-sided tumors, as supported by the patterns of metastasis described in the guidelines 1. This pattern reflects the anatomical lymphatic drainage of the kidney, which explains why metastasis to nodes anterior to the psoas muscle below the kidney is uncommon. The recent update on pretreatment staging of urothelial cancer also highlights the importance of accurate imaging and staging in identifying metastatic disease, including lymph node involvement 1. However, the specific location of lymph node metastasis in kidney cancer, such as the area anterior to the psoas muscle, is not directly addressed in this update, making the NCCN Guidelines for Kidney Cancer the most relevant reference for this question 1. Key points to consider include:

• The anatomical location of the fat anterior to the psoas muscle in relation to the kidney and its fascial envelope
• The typical patterns of lymph node metastasis in kidney cancer
• The importance of accurate imaging and staging in identifying metastatic disease
• The relevance of the NCCN Guidelines for Kidney Cancer in addressing this specific question 1.

From the Research

Lymph Node Metastasis in Kidney Cancer

• The location of fat anterior to the psoas muscle, below the lower pole of the kidney, is part of the perirenal fat, but there is limited information on whether this is a common location for lymph node metastasis in kidney cancer 2, 3.
• Studies have shown that lymph node metastases in renal cell carcinoma often occur in the primary lymphatic sites of each kidney, prior to involvement of the nodes overlying the contralateral great vessel 3.
• The presence of enlarged lymph nodes in renal cell carcinoma does not always indicate metastases, as inflammatory changes and/or follicular hyperplasia can also cause lymph node enlargement 4.
• Lymph node dissection may be beneficial in certain high-risk patients with renal cell carcinoma, but its therapeutic value remains questionable 5.
• Regional lymph node metastasis in renal cell carcinoma is associated with a poor prognosis, and the 3- and 5-year survival rates for patients with lymph node metastasis are generally low 6.

Locations of Lymph Node Metastasis

• Lymph node metastases in renal cell carcinoma can occur in various locations, including the renal hilus, interaortocaval region, and along the great vessels 2, 3.
• The fat anterior to the psoas muscle, below the lower pole of the kidney, is not specifically mentioned as a common location for lymph node metastasis in the available studies 2, 3, 4, 5, 6.

Diagnosis and Treatment

• Preoperative computerized tomography scans can be used to detect enlarged lymph nodes in patients with renal cell carcinoma, but may not always accurately diagnose metastases 4.
• Lymph node dissection may be performed in conjunction with nephrectomy for high-risk patients with renal cell carcinoma, but its role in improving survival is still debated 2, 3, 5.