Cancer Stem-Like Cells Orchestrate Perivascular Dissemination of Malignant Peripheral Nerve Sheath Tumors via Tumor-Associated Macrophages and Astrocytes

Background: Malignant peripheral nerve sheath tumors (MPNSTs) of cranial nerves rare-ly invade brain parenchyma but frequently disseminate along perivascular spaces (PVS). Cancer stem-like cells (CSLCs) drive this process by contributing tumor spread and local microenvironmental disruption. This study investigated the distribution of nestin-positive CSLCs and associated glial–immune responses during PVS invasion in trigeminal MPNSTs. Methods: In an N-ethyl-N-nitrosourea (ENU)-induced rat model, trigeminal MPNSTs de-veloped in 33% of exposed animals. Twenty-seven MRI-detected tumors were histologi-cally analyzed. CSLCs were identified by nestin immunolabeling and butyrylcholinester-ase (BuChE) histochemistry, while microvasculature, tumor-associated macrophages (TAMs), and reactive astrocytes were visualized using LEA-FITC, Iba-1, and GFAP im-munostaining. Results: Tumors extended through leptomeningeal and Virchow–Robin spaces, accom-panied by marked neuroinflammation, astrogliosis, and TAM recruitment (~15% of tumor mass). Nestin/BuChE-positive CSLCs clustered at PVS margins near the glia limitans, and subsets breached the astrocytic barrier, infiltrating adjacent parenchyma in close associa-tion with Iba-1/LEA-positive TAMs. Conclusions: CSLCs exploit PVS as invasive corridors in intracranial MPNSTs. TAMs and astrocytes establish a supportive microenvironment that promotes barrier disruption, immune evasion, and directional tumor spread. This ENU model recapitulates key fea-tures of CNS dissemination and provides a platform to explore the CSLC–TAM–astrocyte axis for targeted therapeutic strategies.