Non-neoplastic tumor associated cysts (TACs) are benign fluid-containing cysts adjacent to, but not within, a neoplasm.
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Pathology
Non-neoplastic tumor associated cysts are most likely represent trapped encysted pools of CSF adjacent to large extra-axial neoplasms. When a tumor grows it traps the CSF between it and the adjacent brain. It is considered a tumor "epiphenomenon".
Radiographic features
Extra-axial non-neoplastic tumor associated cysts are more common than intra-axial, e.g. meningioma, craniopharyngioma, vestibular schwannoma
- smooth well-demarcated cyst
- can be single or multiple
- it abuts the tumor directly
- vary from small to very large size
- enhancement: absent or minimal
Differential diagnosis
- arachnoid cyst
- enlarged perivascular spaces
- cystic neoplasm