Astrocytoma NOS - cystic

Case contributed by Dr Amr Farouk

Presentation

Indolent course of headaches and recurrent fainting attacks.

Patient Data

Age: 25 years old
Gender: Male
MRI

In the left frontal lobe, mainly in a sub-cortical region is an irregular ovoid shaped cystic lesion. It has a smooth outer border and internal nodular inner surface.  It displays low to intermediate signal intensity in T1 and heterogeneous high signal intensity in T2. On post-contrast series, it shows intense marginal nodular non-uniform contrast enhancement (ring enhancement) and central non-enhancing component.  In DWI and ADC, its center shows facilitated diffusion with mild diffusion restriction.  It is surrounded by minimal vasogenic edema pattern. Both exert a mild mass effect in the form of effacement of the overlying cortical sulci & compression on the frontal horn of the ipsilateral lateral ventricle as well as minimal midline shift. Medially the SOL is seen indenting the left frontal rectus gyrus. Posteriorly the SOL is seen buckling the left aspect of the genu of the corpus callosum. It measures about 5.2 x 3.7 x 3.4 cm along its maximum AP, transverse and craniocaudal dimensions respectively. No supratentorial hydrocephalic changes.

A right high parietal convexity extra-axial cyst is seen with no related contrast enhancement or diffusion restriction measuring 2.5X1.9X2.4 cm along its maximum AP, transverse and craniocaudal dimensions respectively (arachnoid cyst).

The MRS voxel was placed at the SOL and showed elevated Cho peak, Cho/NAA and Cho/Cr ratio, moderately elevated Myoinositol peak and elevation of the lipid/lactate peak.

Case Discussion

The differential diagnosis of a cerebral ring-enhancing lesion includes cerebral abscessmetastasisglioblastoma and tumefactive demyelinating lesion (incomplete ring).

No single feature is pathognomonic. Many features of the lesion, as well as clinical presentation and patient demographics, are needed to reach a final diagnosis.

Features in favor of a glioblastoma include thick and nodular wall, restricted diffusion of enhancing wall and absence of central diffusion restriction in addition to spectroscopic findings within the SOL and surrounding edema showing elevation of choline peak, reduction of NAA peak and elevation of lipid/lactate peak. The moderate elevation of myoinositol peak suggest intermediate grade neoplasm.

Lack of thin and regular wall and lack of central restricted diffusion excludes an abscess

Lack of incomplete ring toward the cortex makes tumefactive demyelinating lesion. unlikely.

Lack of multiplicity or significant surrounding edema reduces the likelihood of a metastases.

Histology

The patient underwent surgery and excision with the gross pathology received two specimens 1. Multiple mucoid greyish white and pink tissue fragments of collective size 1.5X1.5 cm. and 2.13 ml of yellowish fluid received in a syringe.

The sections examined of the specimen revealed involvement by the tumor tissue showing diffuse sheeting of relatively cellular atypical astrocytic cells against a fibrillary background. The cells displayed mild atypia. Perivascular lymphocytic infiltrate and focal calcification were seen. Palisading necrosis or endothelial vascular changes could not be seen in sections examined.

The examination of the fluid revealed markedly hypocellular smear with proteinaceous background and few degenerated atypical cells.

The final diagnosis is astrocytoma, grade II, with cystic change. 

Discussion

This is an unusual lesion and the possibility of the samples examined by the histologist being non-representative and resulting in a lower grade needs to be kept as a distinct possibility. Also, given that some calcification was identified the possibility that this represents an oligodendroglioma should also be entertained. In all such cases IDH status needs to be assessed and if mutated (on immunohistochemistry and/or sequencing) then 1p19q status also needs to be performed. Without molecular testing the diagnosis must be based on histology and classified as astrocytoma NOS according to the current WHO classification

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Case information

rID: 59089
Published: 14th Apr 2018
Last edited: 14th Aug 2019
Inclusion in quiz mode: Included

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