Abstract
A male in his late 70s, with progressive hip pain, was diagnosed with a metastatic iliac bone tumor, initially misinterpreted as septic arthritis. Despite extensive imaging, the primary tumor site was undetected until autopsy, which confirmed undifferentiated carcinoma of the liver with secondary lung involvement. The patient's poor performance status and rapid health decline precluded aggressive treatment, leading to his demise. This case underscores the difficulties in diagnosing such carcinomas and suggests that early identification and innovative therapies like nivolumab could potentially extend life in similar cases.