Talar metastasis of mucinous lung adenocarcinoma with fluid–fluid levels: a rare presentation mimicking a benign tumor

The differential diagnosis of bone tumors in the talus is broad and includes both benign and malignant conditions. Metastases, although very rare, are one of these conditions. The typical nonspecific clinical and radiological presentations of metastases are a diagnostic challenge, and a high level of suspicion is needed in order to perform an adequate diagnostic approach. Moreover, they can present with features which have classically been associated with benign conditions such as fluid–fluid levels. We present a rare case of talar metastasis of a mucinous pulmonary adenocarcinoma that presented with fluid–fluid levels and was initially misdiagnosed as a giant-cell tumor with areas of secondary aneurysmal bone cyst transformation.