Periprosthetic metastases in carcinoma of unknown primary: A rare association

Septic or aseptic loosening may cause bone loss around artificial prosthesis leading to prosthesis failure. This occurrence due to metastatic infiltration of bone or surrounding soft tissues is rare but has been occasionally reported. We report a case of an elderly lady presenting with swelling and pain at the site of previous hemiarthroplasty performed for traumatic injury. On evaluation, she was found to have a lytic femur lesion with a large soft-tissue component around the prosthetic joint. Biopsy suggested a metastatic carcinoma of renal origin, but screening of kidneys did not reveal any primary lesion. She had additional skeletal metastatic lesions but no other primary site was detected either. She was given palliative radiotherapy and systemic therapy (sunitinib) based on the histologic diagnosis of renal cell origin but did not tolerate it. Thereafter, she is continuing on zoledronate every 4 weeks and best supportive management since 4 months from diagnosis.