Aggressive vertebral hemangioma: a post-bioptic finding, the gas web sign—report of two cases

Vertebral hemangiomas are relatively frequent among tumors of the spine. Most of them are asymptomatic and the diagnosis is usually made based solely on imaging. However, although rare, some hemangiomas with atypical imaging features (aggressive hemangiomas) can pose a diagnostic challenge. Clinically, these patients present with neurological symptoms. In imaging, aggressive hemangiomas appear as lesions with significant osseous expansion or extraosseous extension, mimicking the appearance of other tumors, such as metastasis or plasmacytoma. In such cases, a biopsy is often required to obtain a histopathological diagnosis in order to rule out the differential diagnoses mentioned above. We report on two cases of aggressive hemangiomas whose diagnosis remained uncertain until the pathology analysis. On CT-scan control immediately after biopsy, we have been surprised to observe the formation of gas bubbles inside the biopsied lesion, spreading over almost the whole vertebra. This gas web sign may support its liquid-filled spaces composition and its benign nature. Our goal was to highlight this finding and its usefulness.