Glioblastoma (GBM) cancer stem cells (CSCs) are insidious. They extensively infiltrate brain tissue, resist radiotherapy and chemotherapy, and are thought to represent the ultimate drivers of disease progression. New research has identified CD109, a GPI‐anchored protein, on a population of perivascular CSCs. Investigation of primary human tumour tissue suggests a role for CD109‐expressing CSCs in the progression from low‐grade to high‐grade glioma, and animal modelling reveals a critical role for CD109 in the maintenance of the GBM CSC phenotype. Furthermore, CD109‐expressing CSCs appear to drive the proliferation of adjacent non‐stem tumour cells (NSTCs) in a rare example of CSC–NSTC cooperative interaction. With this Commentary, we highlight the newly revealed biology of CD109, and offer a synthesis of the published information on glioma CSCs in a variety of anatomical growth zones. We also discuss the landscape of interacting cells within GBM tumours, emphasizing the few reported examples of pro‐tumourigenic, interactive tumour cell partnerships, as well as a variety of tumour cell–non‐transformed neural cell interactions. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.