A 14-year-old girl presents with painless facial asymmetry over the right maxilla. CT shows an expansile lesion with a homogeneous ground-glass matrix blending imperceptibly with normal bone, without cortical destruction. Biopsy shows curvilinear trabeculae of woven bone in a fibrous stroma. The most likely diagnosis is:

• A Ossifying fibroma
• B Osteoblastoma
• C Giant cell reparative granuloma
• D Fibrous dysplasia ✓

Explanation

The ground-glass radiographic pattern with blending into surrounding bone, plus histology showing woven bone trabeculae in cellular fibrous tissue without osteoblastic rimming, is diagnostic of fibrous dysplasia, the commonest site being the maxilla. Ossifying fibroma is distinguished by being well circumscribed with a capsule and radiologically distinct from host bone. Giant cell lesions show multinucleate giant cells, and osteoblastoma has prominent osteoblasts.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.