A rare case of a solitary osseous metastasis from breast carcinoma presenting with fluid-fluid levels on MRI

Osseous metastatic disease is commonly encountered in breast carcinoma, which typically presents as either osteolytic, osteoblastic, or mixed lesions on imaging. Osseous metastasis presenting as a multiloculated cystic lesion with fluid-fluid levels resembling that of an aneurysmal bone cyst (ABC) is sparsely described in the literature, and even less so in the case of breast carcinoma. We report an unusual case of fluid-fluid levels in a bone metastasis to the spine in a 66-year-old female with a prior history of breast carcinoma. Magnetic resonance imaging (MRI) demonstrated a cystic lesion with fluid levels resembling that of an ABC. Computed tomography (CT)-guided biopsy revealed the lesion to be a metastasis from breast carcinoma. The management of ABCs and osseous metastases differ drastically. Accurate diagnosis and distinction between these lesions is paramount as the management of metastatic disease can have a significant impact on the quality and length of life. The presentation, differential diagnoses and imaging features of this atypical case are discussed.