Medulloepithelioma: Two unusual locations.

Reported herein are two cases of medulloepithelioma (ME) occurring in very unusual locations. Case 1 involved a 44-year-old man who presented with leg pain and urinary incontinence. Spine magnetic resonance imaging (MRI) showed an enhancing epidural and intradural lumbosacral mass. He underwent L3-S2 laminectomy with partial tumor resection. Approximately 2 months following surgery, he developed leptomeningeal spread of the tumor, and died 2 months later. Case 2 involved a 22-month-old girl who presented with painless left proptosis. MRI demonstrated diffuse, fusiform, and contrast-enhancing enlargement of the left optic nerve. Following biopsy, she was treated with chemotherapy. Histologically, the tumors in both cases consisted of primitive pseudostratified neuroepithelial cells, arranged in papillary, tubular, or trabecular configurations. A PAS-stained external limiting membrane (ELM) of the neuroepithelia was present. In case 1 there were scattered cartilaginous nodules within the tumor, in keeping with the diagnosis of a teratoid ME. Immunohistochemically, the tumor cells were positive for synaptophysin, nestin, microtubule-associated protein-2, CD56, CD10, glial fibrillary acidic protein (focal), and S-100 protein (focal). The main differential diagnoses include an immature teratoma and an optic nerve glioma in cases 1 and 2, respectively. Histological demonstration of the ELM by PAS stain is a simple but useful technique.