Solitary Plasmacytoma of the Sternum Mimicking Bone Metastasis in a Patient with a History of Breast Cancer Evaluated by F-18-FDG PET/CT.

A 65-year-old woman with a history of breast cancer (stage T2N0M0 treated with left breast conservative therapy 7 years previously followed by hormone therapy) underwent fluorine-18-fluorodeoxyglucose positron emission tomography/computed tomography (F-18-FDG PET/CT) for restaging due to increased serum tumour markers levels (CA15-3, 37 U/ml and CEA, 8 ng/ml). The patient presented thoracic pain before performing F-18-FDG PET/CT. PET/CT demonstrated an area of increased F-18-FDG uptake corresponding to an osteolytic lesion occupying the upper sternum suspicious for bone metastasis (Fig. 1). No other areas of abnormal F-18-FDG uptake were detected in the rest of the body. Based on this PET/CT finding, the patient performed biopsy of the sternal lesion. Histology demonstrated the presence of a sternal plasmacytoma and the patient was addressed to radiation therapy.

Fig. 1

A female patient with a history of breast cancer underwent F-18-FDG PET/CT for restaging due to increasing serum tumour marker levels. Whole-body maximum intensity projection (MIP) F-18-FDG PET image (A) showed an area of moderate F-18-FDG uptake in the thoracic region (arrow). F-18-FDG PET (B1-B3), unenhanced CT (C1-C3) and fused PET/CT images (D1-D3), in axial (B1, C1, D1), sagittal (B2, C2, D2) and coronal (B3, C3, D3) projection showed increased radiopharmaceutical uptake corresponding to an osteolytic lesion of the upper sternum with a maximal standardized uptake value of 4.6, suspicious for a bone metastasis. No other areas of abnormal F-18-FDG uptake were detected in the rest of the body. Based on this PET/CT finding, biopsy of the sternal lesion was performed on the patient. Histology demonstrated the presence of a sternal plasmacytoma and the patient was addressed to radiation therapy

The role of F-18-FDG PET/CT in patients with multiple myeloma is well known [1-4], whereas only some articles evaluated the usefulness of this method in patients with solitary plasmacytomas [5, 6]. In particular, F-18-FDG PET/CT may be useful in demonstrating the evolution of solitary plasmacytomas in multiple myeloma [7].

In our case F-18-FDG PET/CT was useful in detecting a solitary plasmacytoma of the sternum mimicking bone metastasis in a patient with history of breast cancer, correctly addressing to further histological evaluation.