Diagnostic challenges of posterior fossa hemangioblastomas: Refining current radiological classification scheme

Hemangioblastomas (HBMs) are known to exhibit very typical radiological features and thus classified by well-established radiological classification scheme. We reviewed our series of posterior fossa HBMs in order not only to evaluate the relevance of current classification scheme, but also to possibly refine it. Also, we added descriptions on several cases with unusual radiological magnetic resonance imaging (MRI) findings in which differential diagnosis was challenging. We retrospectively reviewed preoperative MRI of 118 patients with pathologically diagnosed posterior fossa HBMs at our institution between 2002 and 2015. Total 128 tumors were included to this study and classified into four categories based on the presence and nature of cystic components: extratumoral cystic (Type Ce, classical cystic with a mural nodule), intratumoral cystic (Type Ci), mixed cystic (Type Cm), and solid (Type S). The association with von Hippel-Lindau (VHL) disease was also investigated. In 118 patients (65 male and 53 female), 79 (66.9%) had solitary HBMs and 39 (33.1%) were diagnosed with VHL disease. Type Ce with typical radiological findings was the most prevalent type of HBM (63.3%), followed by Type S (21.1%). HBMs with intratumoral cysts were uncommon (Type Ci, 11.7%) and mixed extratumoral and intratumoral cysts (Type Cm) accounted for only 3.9%. No intergroup differences were observed in the proportions of each subtype between the solitary and VHL disease-associated HBMs. The blood loss was much lower in Type Ce than in other subtypes. In Type Cm, radical resection was often challenging as the differentiation between intratumoral and extratumoral cysts was difficult resulting in incomplete resection. Refined radiological classification scheme is more practical because it does not only help surgeons determine whether the cystic wall should be removed or not, but also covers cases with atypical radiological presentations. For solid and extraparenchymal HBMs, differential diagnosis is more difficult as well as very critical as surgical removal is often very challenging.