Glioblastoma IDH wild-type (pseudoprogression)

Case contributed by A.Prof Frank Gaillard

Presentation

Headaches, right sided weakness and now drowsy.

Patient Data

Age: 45 years

In the right middle lobe a large cystic mass is present with marked mass effect and contralateral hydrocephalus of the lateral ventricle. 

The patient went on to have emergency surgery without preoperative MRI. 

Histology

MICROSCOPIC DESCRIPTION: The sections show features of a moderately cellular astrocytic tumour. Most of the tumour cells are astrocytic. They have elongated, angulated and pleomorphic nuclei. A second very minor population of neoplastic oligodendroglial cells is also present. These cells have round nuclei and perinuclear haloes. Scattered mitotic figures are identified. There are foci of microvascular proliferation. Areas of necrosis with focal palisading are present. There are perivascular lymphocytes.

The tumour cells are focally p53 positive. IDH-1 and MGMT immunostains are negative (likely methylated). There is no loss of staining for ATRX. The topoisomerase index is about 15%. 

FINAL DIAGNOSIS: Glioblastoma with oligodendroglioma component (WHO Grade IV).

 

Following surgery, the patient had a post-op MRI and was commenced on Stupp protocol combined chemoradiotherapy. 

A right temporal lobectomy and resection of the mass has been carried out with blood product (intrinsic high T1) and no significant residual enhancing tumour. 

MRI

4 months post-op

4 months post op extensive enhancement has develop that appears to fill the resection cavity. It is surrounded by oedema. 

MRI

5 months post op.

There is an extensive high T2 and FLAIR signal abnormalities surrounding the resection cavity and extending superiorly throughout the frontoparietal white matter, as well as a thick linear and irregular contrast enhancement along the resection margins in the temporal lobe occupying the resection cavity. No areas of restricted diffusion; in fact there is strikingly facilitated diffusion. These findings are unchanged compared to the most recent scan, however, are increased compared to the post-operative scan.

Spectroscopy traces reveal increased choline just within the transition of the enhancing margins to the adjacent brain parenchyma; elsewhere the trace is essentially hypometabolic with a dominant lactate peak.

There are just a few scattered foci of increased perfusion, likely vascular. The enhancing component demonstrates low CBV. 

Conclusion: Although residual tumour no doubt is present, in this treatment context, the features suggest pseudoprogression as the dominant process.

MRI

9 months post op

Subjacent FLAIR hyperintensity and enhancement have both decreased since the prior study and there is new ex vacuo dilatation of the right lateral ventricle. No new areas of involvement. A small focus of FLAIR hyperintensity in the left superior frontal gyrus has slightly increased in conspicuity, likely treatment related. Spectroscopy fails to show any significant tumoral trace. No diffusion restriction. No elevated CBV

Conclusion: Improved appearances, suggesting a component of response and/or resolving pseudoprogression.

Case Discussion

This case illustrates the importance taking into account timing of imaging with respect to treatment (pseudoprogression typically occurs in the first three months following completion of chemoradiotherapy (which usually lasts ~3 months)). It is also important to know MGMT status, as methylation significantly increases the likelihood of pseudoprogression occurring. 

 

The diagnosis of GBM is actually not entirely established in this case as the IDH wild-type status has only been inferred with a negative IDH1 R132H immunohistochemistry. Although it is highly likely to reflect true IDH wild-type status, it is possible that this is a non-R132H mutation or an IDH2 mutation. In such cases, when the patient is young IDH sequencing is recommended to prove that no IDH mutation is present. If an IDH mutation was found, then 1p19q codeletion status would also need to be established (intact ATRX suggests 1p19q codeletion). This is important from a classification and prognosis point of view as if an IDH mutation was found and 1p19q was co-deleted then this tumour would actually represent an anaplastic oligodendroglioma and not at glioblastoma. 

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Case information

rID: 44854
Case created: 5th May 2016
Last edited: 22nd May 2017
Inclusion in quiz mode: Included

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