Malignant lymphoma of the cranial vault is a rare entity and the tumor growth patterns are not well understood. Here we report two cases of malignant lymphoma involving the scalp and epidural space with slight changes in the intervening skull. A 63-year-old woman presented with a scalp mass in her right frontal area. Computed tomography (CT) and magnetic resonance (MR) imaging demonstrated mass lesions in the scalp and epidural space with slight osteolytic changes in the intervening skull. She underwent resection of the lesions. A 53-year-old man presented with a mass in his right frontal area. CT and MR imaging showed mass lesions in the scalp and epidural space without changes in the skull. He underwent resection of the lesions. The histopathological diagnosis was diffuse large B cell lymphoma in both cases. Microscopic examination of the intervening skull found that the bone marrow was diffusely replaced by lymphoma cells, and lymphoma cells extended to the extra- or intra-cranial space along the emissary veins without destruction of the cortical or trabecular bone. These histopathological findings explain the radiological findings and provide the clues to elucidate the mechanism of extension of cranial vault lymphoma.
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