Paget's disease of bone with superimposed osseous metastasis from lung carcinoma: A case report.

Paget's disease of bone is a common adult musculoskeletal disorder characterized by disorganized bone remodeling and abnormal bone turnover. Patients with Paget's disease are predisposed to complications including bone pain, pathologic fracture, and malignant transformation. Superimposed metastatic disease within Paget-affected bone represents a diagnostic challenge due to overlapping imaging features. We present a case of a 63-year-old woman with known Paget's disease of the right tibia who was subsequently diagnosed with metastatic non-small cell lung carcinoma (NSCLC). Imaging demonstrated a new lytic lesion in the right proximal tibia with cortical destruction and anterior soft tissue extension, consistent with metastatic disease on a background of Paget's disease. Additional metastatic lesions were identified in the right superior pubic ramus/acetabulum, right posterior seventh rib, and right proximal humerus without associated Paget's disease. The diagnosis of metastatic disease was further supported by biopsy confirmation of NSCLC origin from the acetabular lesion. Due to high fracture risk, the patient underwent prophylactic intramedullary nailing of the right tibia and later required intramedullary fixation of a pathologic right humeral fracture. This case highlights the importance of recognizing atypical imaging findings within Pagetic bone as timely diagnosis of superimposed metastatic disease can significantly impact management.