Diagnostic dilemma in a patient with upper arm mass with history of breast cancer and melanoma

We present a case of upper limb muscle metastasis in a female patient with a history of malignant melanoma. Although melanoma is the fifth most common cancer in the UK, muscle metastases are extremely rare, with only a few cases reported in the literature. We discuss the challenge of diagnosing muscle metastasis on radiological imaging and in particular of distinguishing metastatic lesions to muscle from sarcoma. We also review the imaging findings of other published cases in a literature review. We conclude that although certain characteristic features of melanoma metastases can be identified on imaging (e.g., hyperintensity on T (1)-weighted MRI), the radiological appearances are highly variable and histopathological examination is necessary to confirm the diagnosis.