Unusual Presentation of Ewing Sarcoma in a Nigerian Adolescent: A Case Report and Literature Review

Ewing sarcoma is a malignant, aggressive small, round, blue cell tumour, likely of neural crest origin. It is the second most common bone cancer in children, usually affecting the long bones and central axis. The involvement of flat and irregular bones is rare. We present a Nigerian adolescent male with a three-year history of left foot pain following a minor trauma, a one-year history of foot swelling, and progressive swelling in the left lower limb, scalp, and jaw over seven months. A foot ulcer developed a few days after biopsy. A duplex ultrasound scan revealed multiple enlarged inguinal and popliteal lymph nodes. A head CT scan showed a solitary lytic lesion in the right posterior parietal bone. An MRI of the left foot demonstrated a large soft tissue mass on the first metatarsal with cortical destruction. An initial histopathology diagnosis with open biopsy was Bacillary angiomatosis. Histology of a second open biopsy specimen from the affected foot showed mainly granulation tissues, but a subsequent USS-guided core-needle biopsy of the scalp and jaw masses done one month later revealed a small, round, blue cell tumour. Immunohistochemistry confirmed Ewing sarcoma. The patient responded remarkably to multi-agent chemotherapy, with significant tumour regression and symptom relief. Flat and irregular bone involvement in Ewing sarcoma is rare but possible. This highlights the importance of maintaining a high index of suspicion, utilising appropriate imaging, and ensuring adequate tissue sampling for accurate diagnosis and effective treatment.