An autopsy case of progressive multifocal leukoencephalopathy: comparison of magnetic resonance imaging findings with the pathological findings

A 41-year-old man diagnosed with malignant lymphoma (MLy) in November 2007 developed paralysis that worsened rapidly in January 2008. Magnetic resonance imaging (MRI) showed multifocal T2 high-intensity lesions without edema or gadolinium enhancement in the white matter. The lesions were characterized by a central core with low signal intensity, surrounded by a rim of high signal intensity on diffusion-weighted images (DWIs). At first, we suspected brain metastasis of MLy and used anti-cancer drugs, but the patient's condition worsened. A brain biopsy was then taken to determine whether the patient had MLy metastasis or progressive multifocal leukoencephalopathy (PML) so that an appropriate course of treatment could be determined. The biopsy contained no characteristic nuclear inclusions of PML, but we were able to rule out MLy; therefore, the patient was treated with cytarabine in February 2008, but he died because of sepsis in March. Upon autopsy, many characteristic nuclear inclusions of PML were found in the periphery of the lesions, and in the central core, there was severe demyelinating and tissue softening without typical nuclear inclusions of oligodendroglias. This structure is similar to the structure observed on DWIs, in which a low signal intensity core is surrounded by a rim of high signal intensity. The presence of inclusion bodies in the rim would correspond to the high signal intensity area on DWIs. The peripheral area may have given high signal intensity on DWIs because of the active findings of many swelling oligodendroglias with typical nuclear inclusions. Conversely, the central lesions would give low signals on DWIs because of demyelination and softening. Hence, the region with high signal intensity adjacent to the central low signal area on DWIs would be an appropriate biopsy point for PML diagnosis. ).