Fig. 5

The tumor-like mass reveals osseous metaplasia. A A large focus of metaplastic bone containing marrow-like tissue was present within the fibrotic mass (H&E stain, 40  ×  magnification). B Osteoblasts-rimming woven bones and abundant lipid-laden macrophages are identified in the marrow-like tissue without cellular atypia (H&E stain, 400  ×  magnification; inset: CD68 stain, 400  ×  magnification). C Surrounding the fibro-osseous tissue is gliotic tissue (H&E stain, 400  ×  magnification) D that is highlighted with glial fibrillary acid protein (GFAP) stain. E A monolayer to several layers of cohesive cells lining along the fibro-osseous tissue were identified. These cells displayed cuboidal to columnar shape with some melanin pigments (H&E stain, 400  ×  magnification). F Immunohistochemically they are positive for CK8 (CAM5.2) and negative for CD68 (not shown), suggesting a retinal pigment epithelial (RPE) origin (400  ×  magnification)