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DOI: 10.1148/rg.275075011
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Fourth Ventricle Epidermoid Tumor: Radiologic, Intraoperative, and Pathologic Findings1

Reza Forghani, MD, PhD, Richard I. Farb, MD, Tim-Rasmus Kiehl, MD, and Mark Bernstein, MD

1 From the Department of Radiology, McGill University Health Center, Montreal General Hospital, 1650 Cedar Ave, Room C5-118, Montreal, QC, Canada H3G 1A4 (R.F.); and Division of Neuroradiology, Department of Medical Imaging (R.I.F.), Department of Pathology (T.-R.K.), and Division of Neurosurgery (M.B.), University Health Network and University of Toronto, Toronto, Ontario, Canada. Received January 24, 2007; revision requested March 6 and received April 3; accepted April 3. All authors have no financial relationships to disclose.

Figure 1A
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  		Figure 1a.  Epidermoid tumor depicted on sagittal T1-weighted (a), axial T2-weighted (b, c), axial (d) and coronal (e) gadolinium-enhanced T1-weighted, and axial fluid-attenuated inversion recovery (FLAIR) (f) images. A fourth ventricle mass is seen expanding, distorting, and compressing the brainstem without any evidence of obstructive hydrocephalus, as demonstrated by the normal size of the lateral ventricles superiorly (b). The mass insinuates through the foramen of Magendie (* in a and e) and the foramina of Luschka (best seen on the left in c, d, f; arrowhead in d) and extends into the cisterna magna and caudally to the level of the foramen magnum (a). On T1-weighted images (a, d, e), its signal is only slightly hyperintense relative to cerebrospinal fluid (CSF). On T2-weighted images (b, c), the mass has a hyperintense but heterogeneous signal, unlike the homogeneously high signal intensity of CSF. No significant enhancement is seen, and there is clear failure of suppression of signal on the FLAIR image. This appearance is characteristic of an epidermoid tumor.

 

Figure 1B
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  		Figure 1b.  Epidermoid tumor depicted on sagittal T1-weighted (a), axial T2-weighted (b, c), axial (d) and coronal (e) gadolinium-enhanced T1-weighted, and axial fluid-attenuated inversion recovery (FLAIR) (f) images. A fourth ventricle mass is seen expanding, distorting, and compressing the brainstem without any evidence of obstructive hydrocephalus, as demonstrated by the normal size of the lateral ventricles superiorly (b). The mass insinuates through the foramen of Magendie (* in a and e) and the foramina of Luschka (best seen on the left in c, d, f; arrowhead in d) and extends into the cisterna magna and caudally to the level of the foramen magnum (a). On T1-weighted images (a, d, e), its signal is only slightly hyperintense relative to cerebrospinal fluid (CSF). On T2-weighted images (b, c), the mass has a hyperintense but heterogeneous signal, unlike the homogeneously high signal intensity of CSF. No significant enhancement is seen, and there is clear failure of suppression of signal on the FLAIR image. This appearance is characteristic of an epidermoid tumor.

 

Figure 1C
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  		Figure 1c.  Epidermoid tumor depicted on sagittal T1-weighted (a), axial T2-weighted (b, c), axial (d) and coronal (e) gadolinium-enhanced T1-weighted, and axial fluid-attenuated inversion recovery (FLAIR) (f) images. A fourth ventricle mass is seen expanding, distorting, and compressing the brainstem without any evidence of obstructive hydrocephalus, as demonstrated by the normal size of the lateral ventricles superiorly (b). The mass insinuates through the foramen of Magendie (* in a and e) and the foramina of Luschka (best seen on the left in c, d, f; arrowhead in d) and extends into the cisterna magna and caudally to the level of the foramen magnum (a). On T1-weighted images (a, d, e), its signal is only slightly hyperintense relative to cerebrospinal fluid (CSF). On T2-weighted images (b, c), the mass has a hyperintense but heterogeneous signal, unlike the homogeneously high signal intensity of CSF. No significant enhancement is seen, and there is clear failure of suppression of signal on the FLAIR image. This appearance is characteristic of an epidermoid tumor.

 

Figure 1D
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  		Figure 1d.  Epidermoid tumor depicted on sagittal T1-weighted (a), axial T2-weighted (b, c), axial (d) and coronal (e) gadolinium-enhanced T1-weighted, and axial fluid-attenuated inversion recovery (FLAIR) (f) images. A fourth ventricle mass is seen expanding, distorting, and compressing the brainstem without any evidence of obstructive hydrocephalus, as demonstrated by the normal size of the lateral ventricles superiorly (b). The mass insinuates through the foramen of Magendie (* in a and e) and the foramina of Luschka (best seen on the left in c, d, f; arrowhead in d) and extends into the cisterna magna and caudally to the level of the foramen magnum (a). On T1-weighted images (a, d, e), its signal is only slightly hyperintense relative to cerebrospinal fluid (CSF). On T2-weighted images (b, c), the mass has a hyperintense but heterogeneous signal, unlike the homogeneously high signal intensity of CSF. No significant enhancement is seen, and there is clear failure of suppression of signal on the FLAIR image. This appearance is characteristic of an epidermoid tumor.

 

Figure 1E
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  		Figure 1e.  Epidermoid tumor depicted on sagittal T1-weighted (a), axial T2-weighted (b, c), axial (d) and coronal (e) gadolinium-enhanced T1-weighted, and axial fluid-attenuated inversion recovery (FLAIR) (f) images. A fourth ventricle mass is seen expanding, distorting, and compressing the brainstem without any evidence of obstructive hydrocephalus, as demonstrated by the normal size of the lateral ventricles superiorly (b). The mass insinuates through the foramen of Magendie (* in a and e) and the foramina of Luschka (best seen on the left in c, d, f; arrowhead in d) and extends into the cisterna magna and caudally to the level of the foramen magnum (a). On T1-weighted images (a, d, e), its signal is only slightly hyperintense relative to cerebrospinal fluid (CSF). On T2-weighted images (b, c), the mass has a hyperintense but heterogeneous signal, unlike the homogeneously high signal intensity of CSF. No significant enhancement is seen, and there is clear failure of suppression of signal on the FLAIR image. This appearance is characteristic of an epidermoid tumor.

 

Figure 1F
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  		Figure 1f.  Epidermoid tumor depicted on sagittal T1-weighted (a), axial T2-weighted (b, c), axial (d) and coronal (e) gadolinium-enhanced T1-weighted, and axial fluid-attenuated inversion recovery (FLAIR) (f) images. A fourth ventricle mass is seen expanding, distorting, and compressing the brainstem without any evidence of obstructive hydrocephalus, as demonstrated by the normal size of the lateral ventricles superiorly (b). The mass insinuates through the foramen of Magendie (* in a and e) and the foramina of Luschka (best seen on the left in c, d, f; arrowhead in d) and extends into the cisterna magna and caudally to the level of the foramen magnum (a). On T1-weighted images (a, d, e), its signal is only slightly hyperintense relative to cerebrospinal fluid (CSF). On T2-weighted images (b, c), the mass has a hyperintense but heterogeneous signal, unlike the homogeneously high signal intensity of CSF. No significant enhancement is seen, and there is clear failure of suppression of signal on the FLAIR image. This appearance is characteristic of an epidermoid tumor.

 

Figure 2A
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  		Figure 2a.  DW images (a, b) and the corresponding apparent diffusion coefficient map (c) demonstrate significant areas of restricted diffusion within the fourth ventricular mass (high signal intensity on DW images, low signal intensity on apparent diffusion coefficient map). Pockets of free diffusion (relatively low signal intensity on DW images) are seen within the mass that likely represent CSF channels trapped within the tumor and probably reflect the basis for the absence of obstructive hydrocephalus in patients with these tumors.

 

Figure 2B
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  		Figure 2b.  DW images (a, b) and the corresponding apparent diffusion coefficient map (c) demonstrate significant areas of restricted diffusion within the fourth ventricular mass (high signal intensity on DW images, low signal intensity on apparent diffusion coefficient map). Pockets of free diffusion (relatively low signal intensity on DW images) are seen within the mass that likely represent CSF channels trapped within the tumor and probably reflect the basis for the absence of obstructive hydrocephalus in patients with these tumors.

 

Figure 2C
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  		Figure 2c.  DW images (a, b) and the corresponding apparent diffusion coefficient map (c) demonstrate significant areas of restricted diffusion within the fourth ventricular mass (high signal intensity on DW images, low signal intensity on apparent diffusion coefficient map). Pockets of free diffusion (relatively low signal intensity on DW images) are seen within the mass that likely represent CSF channels trapped within the tumor and probably reflect the basis for the absence of obstructive hydrocephalus in patients with these tumors.

 

Figure 3
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  		Figure 3.  Intraoperative photograph shows an irregularly lobulated, cauliflower-like pearly tumor, an appearance characteristic of an epidermoid.

 

Figure 4A
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  		Figure 4a.  Photomicrographs (hematoxylineosin stain) demonstrate an attenuated squamous epithelium with abundant anucleate squamae (original magnification, x10; a), regular maturation of the epithelial layer (original magnification, x20; b), and many regions containing cell ghosts or "shadow cells" (original magnification, x20; c). Note the absence of dermal appendages. These findings are typical features for a member of the family of pearly tumors (epidermoid tumor).

 

Figure 4B
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  		Figure 4b.  Photomicrographs (hematoxylineosin stain) demonstrate an attenuated squamous epithelium with abundant anucleate squamae (original magnification, x10; a), regular maturation of the epithelial layer (original magnification, x20; b), and many regions containing cell ghosts or "shadow cells" (original magnification, x20; c). Note the absence of dermal appendages. These findings are typical features for a member of the family of pearly tumors (epidermoid tumor).

 

Figure 4C
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  		Figure 4c.  Photomicrographs (hematoxylineosin stain) demonstrate an attenuated squamous epithelium with abundant anucleate squamae (original magnification, x10; a), regular maturation of the epithelial layer (original magnification, x20; b), and many regions containing cell ghosts or "shadow cells" (original magnification, x20; c). Note the absence of dermal appendages. These findings are typical features for a member of the family of pearly tumors (epidermoid tumor).

 




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