Ewing-like adamantinoma.

The Ewing-like variation of adamantinoma is a rare entity, leading to challenge its differential diagnosis, notably with Ewing's sarcoma. We are reporting a case of a 20-year-old male who presented with swelling in the left leg that had progressed over a 2-year period. X-rays revealed a tumour in the tibia that was intracortical, osteolytic, multilocular and invaded the soft tissues. A surgical biopsy was performed. Histopathology examination showed a tumour growth with small round cells expressing CD99. A diagnosis of Ewing's sarcoma was made. Since the patient declined surgical treatment, chemotherapy was administered. Two years later, the patient returned because the tumour had grown in size. A second biopsy was performed. Microscopic evaluation showed a tumour growth with osteofibrous and epithelial components, which expressed pankeratin and vimentin, but was negative for CD99. A diagnosis of Ewing-like adamantinoma was made.