Patellar metastasis of melanoma.

A 52-year old woman with histologically diagnosed melanoma presented to the Institute of Oncology, University of Istanbul, Turkey, for further management in June 2010. The patient had a history of a melanoma on her back, and had undergone wide excision of lesion followed by lymphadenectomy. Her disease stage was Stage III. PET/CT scan was performed to investigate metastatic areas. Increased [18F]-fluorodeoxyglucose accumulation in the posterior of patella was observed with SUVmax (standardized uptake rate) value 14.6 (Figure). Diagnosis of melanoma metastasis to patella was confirmed by histologically. The patient was treated with single-agent temozolomide chemotherapy. No response to chemotherapy was found and she died due to progressive disease after 15 months. Primary intra-osseous lesions of the patella are rare1 and account for 0.12 per cent of all primary bone tumours. Amongst the reported malignant lesions, haemangioendothelioma, lymphoma, osteosarcoma and metastasis are the most common tumours1. Metastasis to the patella is extremely rare in comparison with primary tumours of the patella because it has a relatively poor blood supply, consisting of a few nutrient branches from the collateral vessels of the knee2. Melanoma is well known for its ability to metastasize to virtually any organ or tissue, including some sites rarely seen with other solid tumours3. Similar to rare metastases to the heart, adrenal glands, pancreas, and kidneys, metastasis to patella was earlier detected infrequently (<1%), although these are now identified with much greater frequency with the use of CT scans and PET. In the literature, only a single case report was found4 except our presentation.

Fig

A nodular lesion of soft tissue density on posterior of patella with high FDG uptake in PET images (arrow).