Cauliflower-Like Shaped Osteoma.

Skull osteoma is a benign tumor that slowly and continuously enlarges. It is frequently observed in routine medical practice and many patients show an arc shape. The authors encountered a patient with osteoma with a rare morphology that developed in the occipital region. The patient was a 66-year-old male who had been aware of the presence of a mass in the occipital region for about 50 years, but its uncomfortable feeling had recently increased, and it was resected. The excised tumor showed a pedunculated cauliflower-like shape continuous to the skull. The pathological diagnosis was osteoma. The cause of rare morphologies includes trauma and infection, but this patient had no such past medical history. Since the development site was the occipital region, it was assumed that chronic stimulation caused the rare morphology.