Unique imaging appearance of neurosarcoidosis as a solitary cystic mass with mural enhancement

Background: Sarcoidosis is an idiopathic, granulomatous, and multi-system inflammatory disorder that can also involve the central nervous system in the form of meningeal, parenchymal, or cranial nerve involvement. Imaging findings can be non-specific and may overlap with other inflammatory, infectious and neoplastic processes, and posing diagnostic challenges. Parenchymal involvement in neurosarcoidosis (NS) predominantly manifests as either non-enhancing white matter lesions or as enhancing parenchymal granulomas. Granulomas usually manifest as multiple solid lesions with nodular enhancement. Case Description: A 72-year-old man presented with right-eye visual field changes with the non-contrast head computed tomography showing a large cystic lesion in the left frontoparietal lobe. Subsequent contrast-enhanced magnetic resonance imaging study revealed a large cystic mass with irregular rim enhancement and mural nodule concerning for glial neoplasm. Cyst decompression with biopsy and histopathological analysis revealed gliosis and prominent perivascular granulomatous inflammation with mixed picture of CD4 and CD8-positive cells suggestive of sarcoidosis. Further subsequent work-up showed mediastinal and cervical lymphadenopathy which on biopsy showed non-necrotizing granulomatous inflammation, consistent with sarcoidosis. Conclusion: Herein, we report unique imaging findings of a NS case manifesting as a solitary cystic intraparenchymal lesion with an enhancing nodular component, mimicking primary intra-cranial tumor. This appearance is highly atypical and rarely been reported earlier.