Cerebral metastases: abscess mimic

Case contributed by A.Prof Frank Gaillard

Presentation

Headaches and ataxia.

Patient Data

Age: 70 years

There is an ill-defined hypodense mass centred on the right cerebellar hemisphere, with local mass effect, effacement of the sulci of both cerebellar hemispheres and compression of the fourth ventricle. The result is effacement of the posterior fossa cisterns and inferior descent of the cerebellar tonsils.

The third and lateral ventricles appear enlarged with moderate periventricular hypodensity.

Three peripherally enhancing lesions are noted, the largest of which is located in the right cerebellar hemisphere. It demonstrates irregular peripheral enhancement, central fluid attenuation, with quite prominent restricted diffusion (ADC 570x 10-6 cm2/s). Abundant surrounding vasogenic oedema is present which results in effacement of the fourth ventricle and obstructive hydrocephalous with transependymal oedema. On susceptibility weighted imaging, some patchy low signal is demonstrated at the margins of the lesion, which is incomplete, and associated with intrinsic high T1 signal. This suggests a component of haemorrhage.

The two other lesions are much smaller, one located in the middle frontal gyrus on the left measuring 7 mm, and an other located in the superior parietal lobule also on the left measuring 8 mm. The latter demonstrates intense restricted diffusion, whereas the frontal lobe lesion does not. Both are surrounded by a small amount of a vasogenic oedema. The parietal lesion also demonstrates some punctate regions of susceptibility induced signal loss. No leptomeningeal abnormal enhancement.

Conclusion: Three peripherally enhancing lesions most likely represent metastases with diffusion restriction presumably the result of a blood products. Having said that, cerebral abscesses is the main differential that need to be excluded. 

Case Discussion

The patient went on to have surgery.

Histology

MICROSCOPIC DESCRIPTION: Sections of cerebellar tissue show a cohesive tumour surrounding an extensive areas of central necrosis. Tumour cells form diffuse sheets of cells with abundant eosinophilic cytoplasm, vesicular nuclei and small nucleoli. No glandular or squamous differentiation is seen. Frequent mitoses are present.

Immunohistochemical results show tumour cells stain: CK7+, CK20 focal+, CK5/6+, p40-, TTF1+, NapsinA+ and CD10+; consistent with poorly differentiated primary lung adenocarcinoma.

FINAL DIAGNOSIS: Cerebral metastases: poorly differentiated adenocarcinoma, consistent with a lung primary.

Discussion

Distinguishing metastases from abscess can be difficult when blood product or central necrosis results in low ADC values centrally. A good clue is the morphology of the enhancing component (usually smooth and regular in abscesses) and T2 / SWI dark rim (complete and regular in abscesses). 

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Case information

rID: 47999
Case created: 13th Sep 2016
Last edited: 13th Oct 2016
Inclusion in quiz mode: Included

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