Occipital aneurysmal bone cyst secondary to eosinophilic granuloma

We describe the case of a 2-year-old male patient with an aneurysmal bone cyst (ABC) of the occiput secondary to unifocal eosinophilic granuloma (EG). The lesion presented as a painless mass of the scalp which had grown rapidly over the 2 weeks prior to admission. Radiologically, the lesion was osteolytic and multicystic with fluid-fluid levels. On histology, the cyst wall contained hemosiderin-laden histiocytes, spindle cells, multinucleated giant cells, Langerhans' cells and eosinophils. Surgical treatment consisted of en bloc resection. Fourteen months after surgery, the patient was well with no local recurrence. Association between EG and ABC is rare. To our knowledge, this is the first case involving the skull.