Presentation
Headache.
Patient Data
Hyperdense lobulated mass in the right middle cranial fossa. The differential includes hemorrhagic lesions (e.g. hemorrhagic metastasis or a primary tumor) or an extra-axial mass (e.g. dural mass or cavernous sinus mass).
There is an intraaxial mass within the anterior aspect of the right temporal lobe with surrounding white matter FLAIR signal abnormality extending throughout the right temporal lobe as well as superiorly through the external capsule and posterior limb internal capsule. This lesion demonstrates heterogeneous signal intensity including regions of intrinsic high T1 signal particularly along its medial margin. There are regions of multilobulated T2 hyperintensity along the lateral and posterior margins which do not suppress on FLAIR. There are also regions of extremely low T2 signal centrally and extensive susceptibility artefact. There are differential regions of enhancement, particularly along the lateral aspects of the lesion, consistent with tumor. No ependymal enhancement. DWI signal is difficult to assess in the presence of blood product. Spectroscopy is non-contributory given extensive susceptibility in the region.
No further intra or extra-axial lesion demonstrated. This mass results in partial effacement and distortion upon the temporal horn of the right lateral ventricle. There is approximately 4 mm of leftward shift of the septum pellucidum. There is mild dilatation of the temporal horn of the left lateral ventricle. The lesion contacts the lateral margin of the right cavernous sinus but without evidence of invasion.
Conclusion: Hemorrhagic intra-axial mass within the anterior right temporal lobe. Hemorrhagic metastasis (melanoma) is most likely. Cavernoma is possible, although felt less likely.
Case Discussion
The patient went on to have a resection.
Histology
The sections show features of malignant epithelioid tumor. The tumor forms sheets and nests. The tumor cells have enlarged pleomorphic nuclei, prominent nucleoli and moderate amounts of eosinophilic cytoplasm. Binucleated cells are noted. Scattered tumor cells contain brown pigment in their cytoplasm. No evidence of lymphovascular invasion is seen. Most of the brown pigment is Masson Fontana positive, indicating melanin. Some Perl's stain positive hemosiderin deposits are also seen.
The tumor cells are focally S-100, HMB-45 and tyrosinase positive (melanocytic markers). CAM5.2, AE1/3, CK7, CK20, TTF-1, synaptophysin, melan-A, SOX-10, BRAF-V600E, GFAP, INI-1, p40, CD30, CD31, CD34, CD138, ERG, desmin and myogenin are negative.
Paraffin shavings have been sent for molecular testing. Result summary:
- BRAF Exon 15: No mutation detected. (predicts lack of response to BRAF tyrosine kinase inhibitors)
- NRAS Exon 3 mutation: DETECTED (may respond to MEK inhibitors)
- KIT: no mutation detected
FINAL DIAGNOSIS: metastatic melanoma.
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