A 19-year-old man presents with a slowly enlarging swelling over the middle third of the shin. X-ray shows an eccentric, well-circumscribed lytic lesion in the anterior tibial cortex with marginal sclerosis and small foci of internal mineralisation. Biopsy shows islands of epithelial cells with squamous and basaloid features arranged in strands within a benign fibrous stroma. The most likely diagnosis is:

• A Adamantinoma ✓
• B Osteofibrous dysplasia
• C Fibrosarcoma of bone
• D Metastatic ameloblastoma

Explanation

Adamantinoma is a rare low-grade malignant tumour with a strong predilection for the mid-shaft of the tibia in adolescents and young adults. Its hallmark is a biphasic pattern: epithelial nests with basaloid, squamous, or tubular differentiation set in a benign-looking fibro-osseous stroma. Osteofibrous dysplasia shares the tibial site but is purely fibro-osseous with no epithelial component, which is the discriminating feature against option B.

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.