Cerebral metastasis - melanoma
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A peripherally enhancing mass at the grey-white matter junction of the supramarginal gyrus with significant surrounding edema. Central diffusion restriction is likely secondary to blood products admixed with proteinacous necrotic material.
Conclusion: The differential is primarily that of a hemorrhagic metastasis (e.g. melanoma). A cavernoma would not be expected to have this degree of enhancement or diffusion restriction. An abscess is possible but the degree of signal loss is more consistent with blood than the thin low T2 rim seen in abscesses.
The patient went on to have a resection.
Sections show brain parenchyma with extensive degenerative changes, microglial activation and foamy macrophages. There are separate fragments of necrotic tissue present. A single 2mm fragment of viable tumor composed of epithelioid to spindled cells with abundant pale eosinophilic cytoplasm, oval hyperchromatic nuclei and small nucleoli are present.
Immunohistochemistry shows strong nuclear staining for SOX-10 in the atypical cells seen in the very small tissue fragment. There is also strong cytoplasmic staining for tyrosinase and melan A.
FINAL DIAGNOSIS: extensively necrotic metastatic malignant melanoma.