KeywordsHemangioblastoma, Cyst, Nodule, VHL, von Hippel-Lindau
Hemangioblastoma is a vascular tumor of the central nervous system (CNS). It most commonly occurs within or on the surface of the cerebellum and represents the most common primary tumor of the posterior fossa in adults. Hemangioblastomas may also occur within the spine. Single tumors may be sporadic, but multiple tumors are almost always associated with von Hippel-Lindau (VHL) disease. Sporadic tumors appear in the fifth and sixth decades of life, whereas VHL-associated tumors are detected earlier, in the third and fourth decades. One-third of patients with cerebellar hemangioblastoma have VHL disease. Two-thirds of VHL patients develop hemangioblastomas; thus screening and surveillance programs are required for this population.
Progressive evolution of hemangioblastomas from solid tumor to cyst with mural nodule has been proposed in the literature. Patients typically present with symptoms due to mass effect, most often from an enlarging peritumoral cyst. An understanding of this progression can assist in clinical decisions regarding follow-up intervals and the timing of surgical intervention.
Types of Hemangioblastoma
Hemangioblastomas are traditionally categorized as one of four types by either histology or imaging ( Fig. 16.1 ). Type 1 (5% of posterior fossa hemangioblastomas) is a simple cyst without a macroscopic nodule. Type 2 is a cyst with a mural nodule (60%). Type 3 is a solid tumor without cyst (26%), and type 4 is a solid tumor with small internal cysts (9%). Types 3 and 4 lesions predominate in the spinal cord. Of note, many authors have disputed the existence of type 1 (purely cystic tumors), questioning the quality of presurgical imaging (contrast not given or slice thickness limitations) or detail of histologic sectioning.
Hemangioblastomas are vascular tumors; thus the solid tumor components demonstrate intense enhancement following contrast administration ( Fig. 16.2 ). It should be noted that when a cyst is associated with this tumor, it is a true “peritumoral cyst”; the wall does not enhance and the wall does not contain tumor (see section titled “ Stages of Evolution ,” further on). Hemangioblastomas often have enlarged feeding vessels that may enhance or manifest as serpiginous hypointense flow voids on T2-weighted images ( Fig. 16.3 ).