Bone metastases with "false negative" findings on ¹⁸F-FDG PET/CT in patients with angiosarcoma: A case series with literature review

Rationale:Fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (F-18-FDG PET/CT) is considered a reliable and indispensable imaging method when evaluating distant metastases and clinical staging of angiosarcomas. Here, we report 2 cases of angiosarcoma with bone metastases with "false negative" findings on F-18-FDG PET/CT. Patient concerns:Case 1, a 39-year-old woman, who had undergone mastectomy for primary angiosarcoma 2 years prior, presented with a 5-month history of right coxalgia. Case 2 was a 37-year-old woman, who had undergone mastectomy for primary angiosarcoma 4 months prior. During postoperative follow-up, multiple bone lesions were detected on magnetic resonance imaging (MRI). Diagnoses:Based on the histopathological findings, both cases were diagnosed with bone metastases of angiosarcoma. Although MRI showed multiple bone metastatic lesions, F-18-FDG PET/CT showed no uptake or osteolytic destruction in both cases. Interventions:Weekly paclitaxel was initiated as a salvage chemotherapy in both cases. Outcomes:No uptake or osteolytic lesions were observed on F-18-FDG PET/CT, despite multiple bone metastases detected on MRI. Lessons:False-negative findings on F-18-FDG PET/CT should be considered when evaluating bone metastases of angiosarcoma. Even with negative findings on F-18-FDG PET/CT, open biopsy should be performed if MRI indicates bone metastases.