Case of the Month David Li PGY 2

Case of the Month David Li PGY 2

Initial presentation • 23 -year-old male, previously healthy • Headache, nausea/vomiting over the past few weeks • No medications, no drug use, no relevant family history

CT head

Post-contrast images

Findings • Large mass in the right temporal lobe, predominantly hypoattenuating with a lobulated iso/hyperdense component at its inferior aspect • No intralesional calcifications are present • Mild degree of perilesional vasogenic edema • Moderate heterogeneous enhancement • Significant positive mass effect • MRI was subsequently obtained for further characterization

Axial T 2

Axial T 1 post-gad

DWI

Findings • Essentially confirms the findings on CT – Solid and cystic components, with the solid component demonstrating heterogeneous signal intensity on T 1 and T 2 -weighted images – Heterogeneous enhancement of the solid component

Differential diagnosis • In summary, we have a young patient with a mixed solid/cystic lesion in the temporal lobe • Ddx: – Pleomorphic xanthoastrocytoma (PXA): temporal lobe is a classic location, typical ddx for lesions that are ‘cystic with an enhancing mural nodule’. Usually involves the overlying leptomeninges – Ganglioma: also typically temporal lobe. Positive, but less prominent, contrast enhancement – Dysembryoplastic neuroepithelial tumor (DNET): also typically temporal lobe. ‘Bubbly’ appearance on T 2 WI, and no diffusion restriction – Ganglioneuroma: many also occur outside the brain

Histopathology

Findings • Hypercellular tumor with mixed fibrillary astrocytes and immature ganglion cells • Fibrillary astrocytes show strong staining for GFAP • Findings in keeping with a low grade glioneuromal tumor, specifically ganglioma

Ganglioma • Typical occurrence in the temporal lobe, presenting in children and young adults, commonly presenting as temporal lobe epilepsy • Imaging features range from mixed cystic/solid to predominantly solid, with variable enhancement patterns • Frequently calcified • Solid component is T 2 bright, cystic component is variable; peritumoral edema is minimal/uncommon • Consists of both ganglion cells and glial elements

Ganglioma • Important to list the other important differential diagnoses for a cystic temporal lobe lesion in a young patient, as clinical presentations and imaging appearances overlap a great deal