433 Implications of Contralateral Clear Cell Renal Cell Carcinoma Metastases: A Series of Fifteen Cases

Introduction/Objective Clear Cell Renal Cell Carcinoma (ccRCC) displays synchronous and metachronous metastases to a variety of organs and sites. Contralateral metastases are thought to be uncommon while retrograde metastases are thought to be rare, though the data is sparse. We conducted a pilot study to assess this perception. Methods/Case Report This is a single institution retrospective study conducted over a 12-month period. Results Twenty-seven patients developed metastases, of which 15 (55.6%) were contralateral. Patient ages ranged from 53 to 83-years-old with a M:F ratio of 2:1. Sites of contralateral metastases included the lung (4), hilar lymph node (1), scapula (1), humerus (2), gastrointestinal tract (2), peritoneum (1), adrenal gland (2); two cases were also retrograde to the spermatic cord (1) and femoral heads (1). Four cases were synchronous; eleven were metachronous. Conclusion Our preliminary study suggests that contralateral ccRCC metastases are not uncommon. 55.6% of cases in our series were contralateral, but retrograde spread is rare, including only 7.4% of cases in our study. The spread may occur via the vertebral venous plexus that connects deep pelvic, thoracic, and vertebral plexuses and provides a route for metastatic spread, separate from the lymphatic system. Pathologists should be aware of this plexus as a route of metastatic dissemination.