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AJNR - American Journal of Neuroradiology

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MR Imaging of Pial Melanosis Secondary to a Posterior Fossa Melanotic Ependymoma

Sait Albayram^a, Efsun Urger^a, Buge Oz^b, Ali Kafadar^c, Civan Islak and Naci Kocer^a

^a Division of Neuroradiology, Department of Radiology, Cerrahpasa Medical School, Istanbul University, Istanbul, Turkey
^b Department of Pathology, Cerrahpasa Medical School, Istanbul University, Istanbul, Turkey
^c Department of Neurosurgery, Cerrahpasa Medical School, Istanbul University, Istanbul, Turkey

View larger version (168K): [in a new window]   FIG 1. Contrast-enhanced (A) and nonenhanced (B) T1-weighted axial MR images reveal a posterior fossa mass that extends cranially through 4th ventricle and left cerebellopontine cistern and caudally through foramen magnum. Nonenhanced T1-weighted sagittal MR image (C) shows that a hyperintense melanin-containing mass displaces the medulla oblongata and spinal cord and extends down to the level of the 6th cervical vertebra. T2-weighted axial MR image (D) shows a heterogeneous posterior fossa mass.

View larger version (127K): [in a new window]   FIG 2. Four sequential T1-weighted nonenhanced sagittal MR images (A) show linear high signal intensity on the pial surfaces of the cerebrum, cerebellum, brain stem, and spinal cord secondary to pial melanin accumulation (arrows). T2-weighted axial MR image (B) shows striking signal intensity voids on the pial surfaces of brain stem (arrows).

View larger version (86K): [in a new window]   FIG 3. Photograph of the surgery shows diffuse black and dark brown pigmentation of the pial surfaces of medulla oblongata and medulla spinalis (arrows). C indicates cerebellum; B, bulbus; CS, cervical spinal cord.

View larger version (108K): [in a new window]   FIG 4. A, Microscopy shows characteristic histopathologic features of ependymoma with true rosettes and pseudorosettes, perivascular orientation (hematoxylin-eosin; original magnification x 200). B, Tumor cells have abundant brown melanin pigment (arrows) in the cytoplasm that shows positivity for Masson-Fontana (original magnification x100). C, Brown melanin pigment is also present in the interstitial space of the tumor (arrows; hematoxylin-eosin; original magnification x40).