A rare case of posterior fossa collision tumor involving low-grade astrocytoma and meningioma

Abstract

This case highlights a rare phenomenon, of two benign tumors, a low-grade astrocytoma, and meningioma, occurring simultaneously in the infratentorial compartment. This unique case seeks to add to the current literature on collision tumors. A 25-year-old female presented with a 9-month history of neck pain and right arm weakness. Imaging demonstrated a ring-enhancing cystic lesion in the posterior fossa, with solid enhancing extension into the spinal canal. The main differential diagnosis was an ependymoma. A suboccipital craniotomy, C1 laminectomy and C2-C4 laminoplasty, was performed and revealed two distinct tumor entities. Histopathology revealed that the cerebellar component was consistent with a low-grade astrocytoma and the extra-axial component was a meningioma. Coexisting tumors of different cell lineage and distinct borders, collision tumor, are very uncommon in clinical practice, with most cases diagnosed intra and post-operatively. A complete medical and genetic assessment is critical for the holistic management of these patients.

Keywords: astrocytoma; central nervous system; coexisting; collision tumor; meningioma; posterior fossa.

Figure 1

MRI brain demonstrating cystic posterior fossa mass, with solid component extending past the foramen magnum, down to the level of C3, on sagittal and axial views, respectively.

Figure 2

Intra-operative photography demonstrating cystic component and solid components of tumor pathologies, cyst intact, and cyst aspirated, respectively.

Figure 3

MRI brain with gadolinium, sagittal views T2- and T1-weighted, respectively, demonstrating partial resection of cystic, intra-axial component and complete resection of solid, and extra-axial component of tumor.

Figure 4

Histology imaging demonstrating. (A) Psammomatous meningioma with cellular whorls and psammoma bodies; no atypia or mitoses. (B) Low-grade glioma—a hypercellular tumor composed of glial cells with mild atypia; no necrosis and no mitosis. (C) GFAP positivity in low-grade glioma.