This report describes a rare case of a patient with lipoma presenting with epileptic seizures associated with expanding perifocal edema. The patient was a 48-year-old man who presented with loss of consciousness and convulsions. Magnetic resonance imaging (MRI) revealed a calcified mass in the corpus callosum with perifocal edema causing mass effect. An interhemispheric approach was used to biopsy the mass lesion. Histological examination revealed typical adipose cells, along with hamartomatous components. These components contained neurofilament and S-100-positive structures showing marked calcification. Fibrous cells immunoreactive for α-smooth muscle actin and epithelial membrane antigen proliferated with focal granulomatous inflammatory changes. MIB-1 index was approximately 5% in immature cells observed in granulomatous areas. We thus suspected a coexisting neoplastic component. The residual lesion persisted in a dormant state for 2 years following biopsy. Surgical resection of a lipoma is extremely difficult and potentially dangerous. However, in the present case, the lesion was accompanied by atypical, expanding, and perifocal edema. Surgical treatment was inevitable for the purpose of histological confirmation, considering differential diagnoses such as dermoid, epidermoid, and glioma. In the end, anticonvulsant therapy proved effective for controlling epileptic seizures.