Cerebellar metastasis (cystic appearance)

Case contributed by Bruno Di Muzio
Diagnosis certain


Headache and dizziness. Previous history of breast cancer.

Patient Data

Age: 50 years
Gender: Female

CT Brain


An irregular multicystic mass with peripheral nodular enhancement is demonstrated within the superomedial left cerebellar hemisphere. No hydrocephalus. A solid enhancing left frontal parafalcine nodule is also observed (meningioma?) and small nodule is noted in the left frontal corona radiata.

MRI Brain


Technique: Multiplanar, multisequence imaging has been obtained through the brain including pre and post contrast sequences.

Findings: An irregular multicystic mass with peripheral nodular enhancement is demonstrated within the superomedial left cerebellar hemisphere. The overall lesion dimensions are 23 x 29 x 28mm (AP x trans x CC). There is moderate mass effect on the adjacent cerebellar hemisphere and vermis with FLAIR hyperintensity, as well as compression of the fourth ventricle. No hydrocephalus at this stage. No tonsillar herniation. The lesion does not demonstrate prominent flow voids.

An 8mm ill-defined enhancing FLAIR hyperintense focus is demonstrated at the superolateral margin of the body of the left lateral ventricle. This does not cause significant mass effect. There is also an 8mm homogeneously enhancing extra-axial lesion abutting the anterior falx to the left of midline. Post contrast T1 volumetric acquisition through the brain for the purposes of stereotaxis has also been obtained.

Conclusion: Cystic left cerebellar lesion with mass effect is most consistent with a metastasis. The enhancing focus adjacent to the left lateral ventricle is favored to also represent a metastatic deposit. The left parafalcine lesion likely represents a meningioma (metastasis less likely).

The patient was submitted to a resection of the cerebellar tumor. 

MRI (3 months later)


Since the previous exams, the 6 mm enhancing nodule in the left anterior corona radiata has developed into a multilobulated heterogeneous ring enhancing mass lesion. The right-sided midline shift of 6 mm remains stable. Mild distortion of the abutting lateral ventricle but without hydrocephalus.

At the left anterior margin of the posterior fossa surgical cavity is an ovoid nodule of enhancement measuring 11 x 9 x 10 mm that is cystic inferiorly, with moderate surrounding FLAIR hyperintensity and mild mass effect on the 4th ventricle. There appear to be some tethering of this to the inferior surface of the left tentorium. More ill-defined mild-to-moderate patchy FLAIR hyperintensity surrounds the cerebellar resection cavity.

Tiny focus of FLAIR hyperintensity in the right centrum semiovale, new, non-specific but most likely incidental.

8mm nodule of solid enhancement abutting the left anterior falx with a small dural tail, unchanged is more probably an incidental meningioma, although a small dural metastasis in this context remains a differential.

Conclusion: Findings are in keeping with progressive metastatic disease, with a markedly enlarged left frontal mass with moderate edema. No post-operative MRI available for correlation, but a nodule of enhancement at the anterior cerebellar resection margin is in keeping with either residual and or recurrent metastasis. Unchanged since the earliest available MRI at the left anterior falx is more probably an incidental small left frontal meningioma than a dural metastasis.

MACROSCOPIC DESCRIPTION: 1. "Posterior fossa cystic met": A fragment of soft pink and gelatinous tissue 4mm, for frozen section/smear. FS DIAGNOSIS: Metastatic carcinoma  2. "Posterior fossa cystic met": Two pieces of soft pink tissue 14x7x5mm and 13x5x8mm. The larger piece is bisected.

MICROSCOPIC DESCRIPTION:1,2. The sections show a densely cellular malignant tumor, forming thickened solid trabeculae with areas of necrosis. The tumor cells are basaloid in appearance with high N/C ratio, enlarged hyperchromatic nuclei, small nucleoli and scanty cytoplasm. There are scattered mitoses. No evidence of lymphovascular invasion is seen. The tumor cells are CK7 and c-kit positive. About 20% of the cells are weakly positive for estrogen receptor. GATA-3, PR, HER2 and TTF-1 are negative. The features are consistent with metastatic adenoid cystic carcinoma (solid pattern).

DIAGNOSIS: 1,2. Posterior fossa: Metastatic adenoid cystic carcinoma, consistent with breast primary.

SUPPLEMENTARY REPORT: This tumor shows similar morphology as to the previous breast lesion. The breast lesion is also c-kit positive.

Case Discussion

This case demonstrates a pathologically proven cystic metastatic cerebellar lesion. An incidental solid parafalcine lesion is consistent with a meningioma. 

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