Bony Metastasis to the Radius as the Initial Presentation of a Lung Adenocarcinoma

When considering tumors of the bone, metastatic disease from a distant primary is more common than primary tumors of the bone itself. The commonest sites to which skeletal metastasis occur are in the axial skeleton, and with regard to the appendicular skeleton, metastasis to the forearm bones is uncommon. Almost a third of patients who present with skeletal metastases do not have any evidence of their primary tumor at presentation. We report a case of a 68-year-old female diagnosed with lung adenocarcinoma after presenting with metastatic deposits involving the right radius as the first clinical manifestation of her disease. She presented initially complaining of painful swelling of her right forearm for a duration of one year. Imaging investigations of her right forearm showed an expansile mixed lytic and sclerotic lesion involving the full length of the right radius. A contrast-enhanced computed tomography scan of her chest to investigate the possible site of primary malignancy showed a peripherally located, well-defined, irregularly shaped mass lesion with enlarged mediastinal lymph nodes. A fluorodeoxyglucose positron emission tomography (FDG-PET) bone scan also noted oligometastatic disease in her right proximal humerus. She was started on palliative docetaxel for six cycles with palliative external beam radiotherapy. Although a variety of tumors metastasize to the bone, metastasis to the appendicular skeleton, and in particular the forearm bones, is a rare phenomenon that is poorly described in the existing literature. Skeletal metastasis may also be the primary presenting feature in a minority of cases. Lung cancer is among the more commonly associated primary sites, and further workup should include appropriate imaging to evaluate for a lung primary as well as an FDG-PET/CT or a bone scan to detect occult metastatic disease.