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57-year-old woman with previous history of glioblastoma treated with surgery and adjuvant chemoradiation. 2 years later, followup neuroimaging shows an increased area of contrast enhancement, concerning for tumour recurrence.
Radiation necrosis of the brain is a side effect of therapeutic radiation used in the treatment of brain tumours. Although tumour necrosis is the desired effect of radiation, radiation necrosis refers to an expansile mass of necrosis involving the brain parenchyma that often requires debulking. Radiologically, this often mimics tumour progression/recurrence (“pseudoprogression”). The time interval between radiation and occurrence of radiation necrosis is usually months to years. Microscopically, the necrosis typically involves the white matter and deep cortex, with coalescing areas of coagulative necrosis. Blood vessels are hyalinized, sclerotic, or show fibrinoid necrosis. Characteristically, there is only minimal inflammation of chronic type. Radiation necrosis itself may become life-threatening if the lesion continues to expand, but prognosis is generally dependent on the biology of the underlying tumour that was irradiated.