Malignant Granular Cell Tumor of the Skull Base

Abstract

Malignant granular cell tumors (MGCTs) are extremely rare, high-grade sarcomas of Schwann cell origin. They often metastasize and are associated with short survival. We describe a patient with a large MGCT arising from the suboccipital nerve that eroded the posterior skull base, invaded the perifocal neck muscles, demonstrated perineural extension, and metastasized to regional lymph nodes. A 60-year-old woman with several years' history of neck pain noticed a right-sided suboccipital swelling 4 months prior to seeking medical attention. Magnetic resonance imaging (MRI) showed a 5-cm bone-eroding suboccipital tumor and a second tumor, anterocaudal to this, 4 cm in diameter. The patient underwent surgery. A 4-cm multinodular tumor was removed, freeing it from the internal jugular vein. A 5-cm suboccipital tumor infiltrated the trapezius, semispinalis capitis, and longissimus capitis muscles. The major and minor rectus capitis muscles were completely engulfed by tumor and their attachments to the occipital bone completely eroded. The oblique capitis muscle was infiltrated at its attachment to the C1 transverse process. These muscles were resected with a free margin to remove all tumor tissue. We then removed tumor encasing the right vertebral artery, the medial mastoid process up to the transverse sinus and anteriorly to the stylomastoid foramen, and lastly, the posterior third of the occipital condyle, achieving a gross total removal and no visible residual on postoperative contrast-enhanced MRI. This case represents the first report of resected primary MGCT involving the posterior fossa and arising from the suboccipital nerve.