Co-Occurrence Conundrum: Brain Metastases from Lung Adenocarcinoma, Radiation Necrosis, and Gliosarcoma

Abstract

Non-small cell lung cancer (NSCLC) commonly presents with metastasis to the brain. When brain metastases are treated with stereotactic radiosurgery (SRS), longitudinal imaging to monitor treatment response may identify radiation necrosis, metastasis progression, and/or another primary brain malignancy. A 60-year-old female with metastatic NSCLC involving the brain underwent treatment with systemic therapy and SRS. While some brain metastases resolved, two remaining sites evolved to resemble radiation necrosis on magnetic resonance imaging and spectroscopy. One of those sites was later confirmed to be radiation necrosis after receding with steroids and bevacizumab. The other lesion continued to enlarge and was then surgically resected, pathologically proven to be a gliosarcoma. When scan findings diverge among multiple treated disease sites, imaging should be cautiously interpreted in conjunction with clinical information as well as early surgical consultation for biopsy consideration, especially when there is suspicion of unusual or superimposed pathologies.

Keywords: Brain metastasis; Glioma; Immunotherapy; Lung cancer; Magnetic resonance imaging; Radiation necrosis.

Fig. 1

Serial MRI scans. Timeline of systemic therapies and MRI scan findings, stratified by brain lesion sites. Yellow stars denote treatment by stereotactic radiosurgery at a corresponding time point and lesion.

Fig. 2

Advanced MRI sequences. A Representative magnetic resonance spectra of metabolites in voxels of the right temporal lobe (top) and right cerebellum (bottom) in December 2019. B Dynamic susceptibility contrast magnetic resonance perfusion imaging of the right temporal lobe (top, hyperperfusion outlined by white arrowheads) and right cerebellum (bottom, hypoperfusion outlined by white diamonds) in April 2020.

Fig. 3

Histopathologic assessment of the right temporal lobe lesion. A Hematoxylin and eosin (H&E) stained specimen showing an admixture of tumor cells with astrocytic and spindled morphology (magnification, ×20). B Positive immunostain for GFAP (brown), consistent with glial cells (magnification, ×20). C Positive Masson trichrome stain for abundant collagen deposition (blue), a feature of sarcomatous cells (magnification, ×20). D H&E stained specimen showing necrosis with viable perivascular tumor cells, more characteristic of tumor necrosis than radiation-associated necrosis (magnification, ×10).