Oligodendroglioma (WHO grade II)


Image 1

Clinical History: 
A 30 year old man referred to Neurosurgery for a mass lesion (of the brain) revealed by imaging at an outside hospital.

Oligodendroglioma (WHO grade II)

MR Technique: 
4 mm axial FSE (21 echoes) pre-contrast T2- and post-contrast GRE (FLASH) T1-weighted images are presented, acquired at 3 T on a Siemens Verio MR system. Sequence parameters were TR/ TE = 5500/86 and 250/2.5 respectively. Scan times were 2:22 and 2:08 min:sec.

Imaging Findings:
There is a focal mass lesion within the left frontal lobe anteriorly, involving both gray and white matter. The epicenter is in white matter, and the lesion is somewhat ill defined. These findings, and the configuration of the lesion, are not suggestive of an infarct (the lesion is not wedge shaped, and the involvement is not a typical arterial distribution). There is mild local mass effect, with effacement of some adjacent sulci. There is no significant midline shift. The mass demonstrates heterogeneous, mild contrast enhancement. Findings are most suggestive of a primary brain neoplasm, specifically a glial cell tumor (glioma). The most common such lesion would be an astrocytoma, with the lesion in question demonstrated by biopsy to be an oligodendroglioma. This would be second on the differential diagnosis list for this mass, considering the imaging findings, patient age, and relative incidence of different lesions.

Oligodendrogliomas are well-differentiated but infiltrating (WHO grade II), slow growing tumors that are both cortical and subcortical in location, with the most common site being the frontal lobe. Given their slow growth, a characteristic clue to diagnosis is calvarial erosion or remodeling (absent in this case). Enhancement, which is seen in only 50% of cases, is typically heterogeneous. Calcification may be present on CT. Peak incidence is in the 4th and 5th decades. Other lesions that on MR imaging appear similar include low-grade astrocytomas and gangliogliomas.