Skull Base Tumors

OBJECTIVE

This article reviews the presenting features, molecular characteristics, diagnosis, and management of selected skull base tumors, including meningiomas, vestibular schwannomas, pituitary neuroendocrine tumors, craniopharyngiomas, chordomas, ecchordosis physaliphora, chondrosarcomas, esthesioneuroblastomas, and paragangliomas.

LATEST DEVELOPMENTS

Skull base tumors pose a management challenge given their complex location and, as a result, the tumors and treatment can result in significant morbidity. In most cases, surgery, radiation therapy, or both yield high rates of disease control, but the use of these therapies may be limited by the surgical accessibility of these tumors and their proximity to critical structures. The World Health Organization classification of pituitary neuroendocrine tumors was updated in 2022. Scientific advances have led to an enhanced understanding of the genetic drivers of many types of skull base tumors and have revealed several potentially targetable genetic alterations. This information is being leveraged in the design of ongoing clinical trials, with the hope of rendering these challenging tumors treatable through less invasive and morbid measures.

ESSENTIAL POINTS

Tumors involving the skull base are heterogeneous and may arise from bony structures, cranial nerves, the meninges, the sinonasal tract, the pituitary gland, or embryonic tissues. Treatment often requires a multidisciplinary approach, with participation from radiation oncologists, medical oncologists, neuro-oncologists, and surgical specialists, including neurosurgeons, otolaryngologists, and head and neck surgeons. Treatment has largely centered around surgical resection, when feasible, and the use of first-line or salvage radiation therapy, with chemotherapy, targeted therapy, or both considered in selected settings. Our growing understanding of the molecular drivers of these diseases may facilitate future expansion of pharmacologic options to treat skull base tumors.

Pearls and Pitfalls in Interpretation of 68Ga-DOTATOC PET Imaging

DOTA-D-Phe-Tyr-octreotide labeled with Ga (Ga-DOTATOC) is the commonly used PET tracer for imaging meningioma because of its high affinity to somatostatin receptor subtype 2 (SSTR2) and an established imaging modality for planning radiation and radionuclide therapy. However, SSTR2 is not an exclusive marker for meningioma, and not all meningiomas express high levels of SSTR2. The SSTR2 expression has been reported in other intracranial tumors, for example, glioma, pituitary adenoma, medullablastoma, primitive neuroectodermal tumors, and hemangioblastoma leading to a significant risk of misinterpretation of PET/CT findings. We present 2 cases with similar Ga-DOTATOC uptakes in 2 distinct etiologies, for example, cerebral lymphoma and meningioma.

Neuroglial ectopia of the vestibular nerve masquerading as a vestibular schwannoma: A case report

Neuroglial ectopia is a rare entity of undetermined clinical significance. Here, we report a unique case of neuroglial ectopia of the vestibular nerve. A 27-year-old pharmacy student with a previous radiological diagnosis of vestibular schwannoma presented to our clinic for surgical evaluation. Magnetic resonance imaging (MRI) of the brain revealed a 17-mm T1 hypo- to isointense, T2 iso- to hyperintense, poorly enhancing left cerebellopontine angle mass extending into the left internal auditory canal compatible by imaging with a vestibular schwannoma. The lesion was resected under MRI guidance. The frozen specimen came back as a benign hypocellular lesion. Histological assessment revealed a peripheral nerve engulfed by glial fibrillary acidic protein-positive, S-100-negative cells, suggestive of neuroglial ectopia. There was no evidence of schwannoma. The main concerns were benign neoplasm with potential for progression or sampling artifact. The patient had an uncomplicated hospital course. This case report demonstrates an unusual case of neuroglial ectopia of the vestibular nerve. The differential diagnoses for a poorly enhancing cerebellopontine angle mass should include neuroglial ectopia.