PMC4198779_01
A representative axial slice from the patient's radiation plan is shown. The left temporal lobe of the brain is contoured in black. This area received 1678 centi-nGy and falls between 1500 centi-nGy (pink) and 1748 centi-nGy (orange) isodose lines. The treatment isocenter received a total dose of 1819 centi-nGy.
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She received 16 fractions of 1.15 neutron nGy/fraction over four weeks for a total dose of 18.4 nGy (Figure 1).
Axial slices of T1 postcontrast (a) and T2 FLAIR (b) MRIs are shown, corresponding to the radiation plan seen in Figure 1. Additional axial T1 postcontrast (c), axial T2 FLAIR (d), coronal T1 postcontrast (e), and sagittal T1 postcontrast (f) slices depict an irregularly enhancing mass lesion in its greatest dimensions, involving the left temporal lobe tip. The lesion measured 4.6 cm in the greatest dimension with significant surrounding edema. There was evidence of temporal bone resection, consistent with prior resection of the left parotid gland.
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However, radiation necrosis was also considered part of the differential diagnosis given there was enhancement in an area corresponding to the original radiation plan (Figure 2).
Axial T1 postcontrast (a), T2 FLAIR (b), coronal T1 postcontrast (c), and sagittal T1 postcontrast (d) MRIs obtained on postoperative day 1 demonstrated total resection of the enhancing mass seen on preoperative imaging. There were some minor blood products and enhancement, consistent with expected normal reactive change after surgery.
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A left temporal craniotomy was performed with gross total resection of the lesion (Figure 3).
Formalin fixed, paraffin embedded tissue sections stained with hematoxylin and eosin demonstrate reactive astrogliosis, radiation-induced vasculopathy, and necrosis. (a) Reactive astrocytes show hypertrophic, eosinophilic cytoplasm with eccentrically placed nuclei. (b) Higher magnification of inset in (a). (c) Hyalinized arterioles are seen, characteristic of radiation-induced vasculopathy. (d) Higher magnification image of (c). Radiation necrosis is demonstrated at (e) interface of brain and necrotic area and (f) necrosis in the center of the lesion.
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Final pathology demonstrated reactive astrogliosis and hyalinized arterioles, characteristic of radiation necrosis, with no evidence of tumor (Figure 4).