Solitary amyloidoma related to THA.

Amyloidoma of soft tissues is rare, and no previously published reports describe it in relation to hip prostheses. This article presents the case of a 78-year-old woman with a medical history of myelodysplasia and mild renal failure who underwent a right-sided metal-on-polyethylene total hip arthroplasty in 2003. She presented to the outpatient clinic with a 1-year history of right anterior thigh pain. On examination, a large proximal anteromedial lump was palpable and was nontender, nonpulsatile, and firm. She had a positive Trendelenburg test but good hip range of motion. Plain radiographs showed signs of osteolysis around the hip prosthesis. Serology showed mildly raised liver function and renal function but a normal erythrocyte sedimentation rate and white blood cell count. Magnetic resonance imaging revealed a large mixed-signal soft tissue mass directly opposing the anterior cortex of the right femur, related to the hip prosthesis, measuring 16×10×7 cm. Associated destruction of the underlying cortex existed. Histological staining of a biopsy of the mass confirmed that the mass contained AL-type amyloid seen in primary amyloidosis. Mean patient age at diagnosis for amyloid tumors of soft tissues is 66 years. By definition, they start as solitary lesions. The types are important: AA type is related to infection and AL type is a primary process. Patients with AL amyloidomas have a poorer prognosis because they have a higher chance of malignancies. Early diagnosis can prevent long-term serious consequences of this condition.