Intraosseous Lipoma with Subsequent Esophageal Carcinoma Metastasis

Background: This case report describes a well documented proximal femoral metadiaphysis intraosseous lipoma which later developed metastasis from a new esophageal cancer. Metastatic disease to benign conditions is a rare finding. To the best of our knowledge, this is the first reported case of metastatic disease to an intraosseous lipoma. Case Description: The metastatic deposit was initially detected by plain-film radiography, performed to evaluate new onset right hip pain, as possible new cortical breakthrough with irregularity in the site of previously known proximal right femur intraosseous lipoma. Concurrent follow-up PET/CT study showed a new hypermetabolic focus within the known intraosseous lipoma indicating a new metastasis that was confirmed with an MRI as a new enhancing mass within the preexisting intraosseous lipoma. Subsequently, an MRI-guided biopsy and eventually surgical excision was performed providing the histological samples for radiologic-pathologic correlation. Purpose and Clinical Relevance: Clinicians need to be aware that unusual, complex patterns within benign lesions may be a reflection of unexpected conditions, such as insufficiency injury, malignant transformation and secondary metastatic disease, as exemplified by our case report.