An asymptomatic hypertrophic pacchionian granulation simulating osteolytic lesion of the calvaria.

Osteolytic lesions can be seen in various diseases. We present a rare case of symptomatic hypertrophic pacchionian granulation mimicking bone tumor in the calvaria. A 50-year-old woman suffered from a previous VII cranial nerve peripheral paresis accompanied by headache. A plain radiograph revealed a punched-out paramedial occipital lesion. Precontrast-enhanced computed tomographic scans demonstrated a hypodense mass, with a defect of both tables of the left occipital bone. Magnetic resonance imaging (MRI) demonstrated a hypointense mass on the T1-weighted image and isointense to cerebrospinal fluid on the T2-weighted image, with capsule-like contrast enhancement by gadolinium. A biopsy was performed. Histologically, hypertrophic pacchionian granulation was diagnosed. The patient has had no growth for 2 years. This case suggests the need to include hypertrophic pacchionian granulation in the differential diagnosis of punched-out lesions.