Images show trabecula of bone with minimal osteoblastic rimming and intervening bland spindle cells. These features are good for fibrous dysplasia. However, the diaphysis of the tibia is the classic site for both adamantinoma of bone and also osteofibrous dysplasia (OFD). I think OFD is the best fit here. A keratin immunostain will often highlight scattered spindle cells, a common finding for OFD. Many believe that OFD is a precursor/on a spectrum with adamantinoma of bone.

middle of shaft of tibia
lamellar bone trabeculae covered by osteoblasts

*interconnected bone trabeculae are mostly lamallar rather than than weaven
* bone trabeculae covered patchily by osteoblasts ( non activated ).
*mass located at commnon site diaphysis of tibia

micro:
-thinned bone trabeculae
-irregular cement lines
-osteocytes
-focal new bone formation
-no osteoblast rimming
-intertrabecular cellular fibrous tissue with blood vessels

clinical:
if one bone only - monostotic form
possible link to endocrinopathies

disorder of maturation of osteoblasts

Radiology:
-radiolucency ground glass like
-scalloping of endosteum

However, in this case, the XRay does not look typical to me...

Differential diagnosis
Fibrous cortical defect/non ossifying fibroma

however, no storiform intertrabecular fibrosis, plump fibroblasts versus spindle fibrocytes...

Fibrous dysplasia. Minimally atypical stroma with boney trabecular lacking osteoblasts lining cells. definitive dx??

Osteoblastoma

Benign. Is it osteoblastoma?

Fibrous dysplasia.