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Fig. 3 | BMC Musculoskeletal Disorders

Fig. 3

From: Bizarre parosteal osteochondromatous proliferation (Nora’s lesion) affecting the distal end of the ulna: a case report

Fig. 3

Gross and microscopic findings for the resected surgical specimen. a The gross photograph of the specimen shows that the surface of the lesion is covered by a cartilage cap and its interior is composed of osteoid tissue in continuity with the cortical bone. b Hematoxylin and eosin (H&E) staining of the tumor sections (magnification 40×). Cartilage was present at the margins of the lesion, and bone formation (asterisk) was found at the center of the lesion at its base fixed to the ulna. Bone trabeculae showed an irregular distribution, some of which was basophilic and incompletely ossified. There was also an area composed of a mixture of bone, cartilage, and fibrous granulation tissue that resembled a fracture callus. Fibrous vascular tissues were arranged loosely among the trabeculae, with little myeloid tissue. c H&E staining of the tumor sections (magnification 40×). The marginal cartilage (asterisk) was not the hyaline cartilage usually seen in the cartilage cap of osteochondromas, but resembled reactive fibrocartilage. d H&E staining of the tumor sections (magnification 200×). e Higher magnification views of the boxed areas of Fig. 3c. In some areas of the views with increased cellularity, star-shaped or spindle-shaped atypical cells were scattered in a somewhat myxomatous background (arrows). f H&E staining of the tumor sections (magnification 100×). Some of the chondrocytes exhibited mild atypia, such as nuclear enlargement and binucleation, without neoplastic osteoid production

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