A 75-year-old man with a medical history including type 2 diabetes mellitus with diabetic nephropathy, stage-1b primary renal cell carcinoma, and a left kidney transplant presented to our hospital after falling on ice. He reported antecedent right thigh pain before the fall. The physical examination was notable for diffuse swelling of the entire right lower extremity. Radiographs showed multiple lytic lesions in the distal right femoral metaphysis and a pathologic fracture of the right proximal tibial shaft (Figs. 1-A and 1-B). Before his presentation, the patient was presumed to be in remission from renal cell carcinoma by his medical oncologist, with the most recent treatment occurring 2.4 years previously.
The patient’s workup included a bone scan that showed increased radiotracer uptake in the skull, thoracic and lumbar spine, sternum, left proximal part of the humerus, left elbow, bilateral sacroiliac joints, right proximal and distal parts of the femur, and proximal part of the tibia. A computed tomographic (CT) scan of the chest, abdomen, and pelvis revealed numerous pulmonary nodules, bilateral hilar lymphadenopathy, multiple subcutaneous nodules, abdominal and pelvic ascites with associated atelectasis, and bilateral pleural and innumerable bony metastases. A magnetic resonance imaging (MRI) scan of the right thigh revealed a well-defined fat signal mass in the vastus lateralis, superolateral to the distal femoral metastases. It contained small foci of low T1 and bright T2 signal and enhancement on postcontrast sequences (Fig. 2).
Surgical repair of the patient’s pathological fractures and removal of the soft-tissue lesion were planned for the same operation, and the patient underwent open biopsy with an intraoperative frozen section of the femur, followed by fixation of the right femur and tibial pathologic fractures (Figs. 3-A, 3-B, and 3-C). However, prior to fracture fixation, the patient underwent marginal excision of the mass to ensure no cross-contamination between the femoral lesion and the soft-tissue mass (Fig. 4).
The outer surface of the fatty, soft-tissue mass was smooth, and sectioning revealed tan-yellow lobulated cut surfaces with multiple well-circumscribed hemorrhagic nodules ranging from 0.3 to 0.7 cm. The histology of the mass is shown in Figures 5-A and 5-B.
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