Tumefactive demyelination and glioblastoma: a rare collision lesion.

OBJECTIVE: Inflammatory demyelination occasionally forms a solitary mass lesion clinically and radiographically indistinguishable from glioma, replete with enhancement and mass effect. Termed "tumefactive demyelination" it often prompts a brain biopsy.
DESIGN: We undertook neuroimaging and morphologic analysis of a unifocal demyelinating lesion intimately associated with glioblastoma. MRI characteristics of the lesion were assessed as were biopsy and resection specimens by both histological and immunohistochemical methods.
RESULTS: The patient, a 49-year-old woman, presented with subacute onset headaches. An MRI T1W scan revealed a hemispheric mass with centrally reduced signal and ring enhancement. T2W images showed increased central signal with a rim of reduced signal co-localized to the enhancing ring. A biopsy was initially misinterpreted as demyelination alone, given abundance of histiocytes, the presence of hypertrophic astrocytes with micronuclei ("Creutzfeldt-Peters cells"), and occasional mitoses. Upon consultative review, two histologically distinct components, one inflammatory demyelination and the other an anaplastic astrocytoma were revealed. Subsequent complete resection of the abnormality demonstrated a WHO grade IV astrocytoma (glioblastoma multiforme).
CONCLUSION: Our experience underscores the importance of adequate tissue sampling during biopsy for suspected glioma, and confirms the fact that active inflammatory demyelination may coexist with a high-grade glioma. Despite detailed study, the basis for the association remains elusive.