Occult renal cell carcinoma with acrometastasis and ipsilateral juxta-articular knee lesions mimicking acute inflammation

Abstract

Generally, skeletal peripheral metastases below the elbow and the knee are rare. Skeletal metastases to the hand or foot are very rare; but when they do it may be a revealing clinical finding. Purely lytic lesions are commonly seen in metastases from lung, renal, and thyroid tumors, but they are also known to occur in primary myeloma, brown tumor and lymphomas. A 70-year-old man was brought to the emergency department with acute painful swelling involving his right hand and the right knee. Due to significant accompanying soft tissue swellings cellulitis, acute osteomyelitis and gouty arthropathy were included in the initial differential diagnosis. Radiographs showed pure lytic bony lesion with complete disappearance of lower two third of the second metacarpal, trapezium and trapezoid bones of the right hand along with a lytic subarticular lesion of medial condyle of ipsilateral femur. Chest X-ray (CXR) was normal but sonography of the abdomen readily demonstrated a large renal mass, later confirmed at biopsy as renal cell carcinoma (RCC). Clinicians should be cognizant of the strong association between digital acrometastases and renal cell carcinoma in male patients with normal CXR findings. In suspected hand acrometastasis associated with a soft tissue component outside the contours of normal bone, screening the abdomen by sonography should be done prior to bone biopsy and before costly or time-consuming investigations are offered. Metastatic RCC should be included in the differential diagnosis of all unilateral expansile bony lesions of the digit. It is particularly important if such lesion/lesions are accompanied by local inflammation. Screening the abdomen by sonography may be of particular value in such elderly male patient when Chest X-ray shows no abnormality.