Answer and Discussion of Quiz Set: N-007

3.    A well-circumscribed non-infiltrating tumor near the foramen of Monro, as evaluated by MRI, was resected from a 48 year-old woman. Histologically, the tumor has a mucoid stroma populated by nests and cords of peithelioid cells. Prominent lymphoplasmacytic infiltrates are also present. In some areas, the tumor is rimmed by areas with non-tumoral piloid gliosis which reflects the well-circumscribed nature as assessed by MRI. There is no mitotic figure present. The tumor cells are positive for glial fibrillary acidic protein (GFAP) and CD34, negtative for synaptophysin, cytokeratin, epithelial membrane antigen (EMA), CD18, or brachyury. Which of the following is the correct diagnosis?   Answer

A.  Chordoid meningioma, WHO grade II

B.  Chordoid glioma, WHO grade II

C.  Clear cell ependymoma

D.  Chordoma

E.  Central neurocytoma with mucoid changes

Answer and Discussion: The answer is (B). Chordoid glioma is positive for GFAP and membranous pattern of immunoreactivity for CD34. These tumors are negative for EMA< CD18, synaptophysin, or brachyury. Chordoid meningioma is often, but not always, positive for EMA but typically negative for GFAP. Clear cell ependymoma is often, but not always, positive for EMA and usually positive for GFAP. They are negative for CD34. The histologic features are also not infavor of clear cell ependymoma. Chordoma is typically positive for brachyury and cytokeratin but negative for GFAP. Neurocytoma is positive for synaptophysin and negative for GFAP.