Presentation
First episode of generalized seizure in previously healthy male. GCS 15 and normal neurology post-seizure. Seizure substrate?
Patient Data
Ill-defined area of gyriform hyperdensity of the inferior right frontal lobe. Several small subtle areas of hyperdensity overlying the left frontal lobe. Mild diffuse sulcal narrowing involving the left frontal lobe. No intra-axial mass or hydrocephalus.
Diffuse nodular areas of high T1 signal on the surface of sulci and gyri predominantly involving the anterior left frontal and temporal lobes. Gyriform area of high T1 signal involving the right inferior frontal lobe, which also displays blooming on SWI suggestive of hemorrhage. Mild sulcal effacement of the left frontal and temporal lobes.
No leptomeningeal or pachymeningeal enhancement. No ventricular dilatation or ependymal enhancement.
MICROSCOPY 1. to 3. Biopsies are from one intraoperative lesion and are described together. There is a pleomorphic neoplasm infiltrating the leptomeningeal space and extending into the cortex along Virchow-Robin space (also seen in specimens 2 and focally in specimen 3). The cells show nuclear pleomorphism with eosinophilic nucleoli and cytoplasmic melanin, and form sheet-like nodules with brain invasion. No necrosis is present and mitotic figures are not seen (0/10 HPF). The neoplastic cells express SOX10 and HMB45 (majority of cells). Ki67 proliferation index is estimated at 5%. The neoplasm shows pleomorphic melanocytes with leptomeningeal spread and brain invasion. The features are of leptomeningeal melanomatosis. Radiological features in favor of metastatic disease is noted, and the differential diagnosis with a primary process is not completely excluded on this histology. Clinical correlation is required.
SUPPLEMENTARY REPORT: c-Kit staining requested by clinician. c-Kit staining is positive.
SUMMARY 1.-3. Cortex, left frontal lobe; Parenchyma, left frontal lobe; Deep lesional tissue - Leptomeningeal melanomatosis, please see description
Report prepared by Dr. Ming Yu, Consultant Pathologist
Case Discussion
This case demonstrates seizures due to leptomeningeal melanomatosis as the presenting clinical sign of presumed metastatic melanoma. CT, FDG PET-CT, and clinical examination revealed no further disease; however, the genetic profile of the melanoma suggested metastatic rather than primary meningeal disease.
The patient unfortunately passed away 5 months after first presentation.