29 Year‐Old Man with New Onset Seizures

Clinical History and Neuroimaging

The patient is a previously healthy 29‐year‐old man who was admitted to our hospital for evaluation after experiencing seizures. A neurological examination elicited no abnormalities. CT and MR imaging were performed and revealed a cortico‐subcortical lesion mass involving most of the right frontal lobe with sulcal effacement, compression on the foramen of Monro and hydrocephalus. The CT demonstrated curvilinear narrow calcifications. The lesion was hyperintense to the cortex on T2 and FLAIR while partially hyperintense on T1, with marked homogeneous enhancement (Figure 1a). All the sequences showed a “bag‐of‐worms sign” (which is best seen on the T2‐weighted images) due to the presence of multiple tiny vessels associated with flow‐voids. Moreover, in the lesion there were two deeply seated pseudocysts that showed contrast enhancement visible in the late phase. Based on these findings, a digital subtraction angiography (DSA) was performed which confirmed the hypervascular nature of the lesion but it did not indicate the presence of an arteriovenous malformation (Figure 1b). At surgery, the lesion was removed via a right frontal craniotomy. The excision was macroscopically complete.

Figure 1a–f.

 

Microscopic Pathology

H&E stains showed a highly cellular neoplasm composed of uniform and monomorphic neoplastic cells; the nuclei were round and perinuclear halos were present (Figure 1c). Numerous calcification were present in the midst of the tumor. The neoplasm showed delicate capillaries disposed in a chicken‐wire pattern and above a diffuse hypertrophic vasculature (Figure 1d). There were some foci of necrosis with areas of vascular proliferation (Figure 1e). Immunohistochemistry evaluation demonstrated positivity for IDH1 antibody demonstrating the presence of an IDH1 (R132H) mutation (Figure 1f). What is the diagnosis?

Diagnosis

Anaplastic oligodendroglioma (WHO III).

Discussion

Anaplastic oligodendroglioma is a highly cellular diffuse infiltrating glioma. Patients with anaplastic oligodendroglioma are likely to respond to chemotherapy 5. Oligodendrogliomas are made up of round cells, usually with a classic “fried‐egg” appearance, with delicate branching capillaries (“chicken‐wire”). In high‐grade tumors there is often vascular proliferation with necrosis.

Co‐deletion of 1p/19q is a hallmark of oligodendrogliomas and has been reported in 50% to 80% of cases with frequencies as high as 90% when using strict diagnostic criteria 1. 1p/19q status is a predictive marker of response to PCV chemotherapy and is also a prognostic marker 1. Moreover, IDH1 mutations are common in oligodendrogliomas and are strongly associated with 1p/19q codeletion and MGMT promoter methylation 8. However our case showed negativity for 1p19q codelation and presence of MGMT methylation.

Radiologically, anaplastic oligodendroglioma presents as a calcified cortical‐subcortical frontal lobe mass. Calcifications are seen in 90% of oligodendroglioma, (the most common glioma to present this feature); the calcifications can be nodular or gyriform. Cystic degeneration is also frequently noted 4 and blood products may be seen. Anaplastic oligodendroglioma enhances much more commonly than low grade oligodendroglioma.

The case herein presented showed some oligodendroglioma featuresbut the marked vascularity, the gyriform calcifications and the cystic degeneration are all features of brain AVMs. The presence of solid enhancement, which is lacking in AVM, allowed the radiological presurgical diagnosis of high grade glioma.

The association of AVMs with brain neoplasms is extremely rare, and data are limited to case reports. Also a glial tumor mimicking AVM has been previously reported 2. The association of AVM and a cerebral glioma has been reported infrequently 3, 7. Usually these two diseases are sufficiently distinctive histologically to cause no diagnostic difficulty. Their potential coexistence in the same lesion requires careful scrutiny to avoid over‐interpretation. Also, the presence of swollen oligodendroglial cells in AVM is quite common and should not be mistaken for tumor cells. They are usually scattered through the lesion, admixed with reactive astrocytes, and are interpreted as being part of the reactive process 3. Regarding the association between gliomas and AVM, a few different conditions should be considered, which are a hypervascularized glioma and coexistence of an AVM with a glioma in two adjacent contiguous regions 6, 7.

The marked vascularity seen on the MRI, the gyriform calcifications and the cystic degeneration are all features which can be encountered in brain AVMs. The presence of solid enhancement, allowed the radiological presurgical diagnosis of high grade glioma. This case illustrates that highly vascular malignant gliomas can simulate vascular lesions by radiology and may require an angiogram for diagnosis.

Abstract

Imaging of a 29‐year‐old man with seizures showed a frontal lobe mass with curvilinear narrow calcifications, cystic components and multiple flow‐voids. An AVM was considered. A DSA confirmed the hypervascular nature of the lesion. It was resected and microscopic examination showed an anaplastic oligodendroglioma remarkable for a diffuse and hypertrophic vasculature with areas of frank vascular proliferation. The marked vascularity seen on the MRI, the gyriform calcifications and the cystic degeneration are all features which can be encountered in an AVM. This case illustrates that highly vascular malignant gliomas can simulate vascular lesions by radiology and may require an angiogram for diagnosis.