The patella as an unusual site of renal cell carcinoma metastasis

We report a rare case of renal cell carcinoma with metastasis to the patella in a 49-year-old man, who presented with seven months of left knee pain after a fall. Only two similar cases have been reported. Patellar metastasis is rare because it has a relatively poor blood supply and microemboli would have been sieved out by the pulmonary circulation. Patellectomy is the usual treatment for such cases. We suspect that the preferential metastasis in our patient is a result of tropism. Our treatment for this patient is unique. We opted for a patella-preserving operation involving the use of cryotherapy, as this treatment modality preserved the quality of life. An opportunistic biopsy one year later confirmed the absence of active disease within the patella. This case uniquely provides human in vivo histological confirmation that an intralesional procedure with local and systemic adjuvant therapy effectively controls local disease.