Evidence-based clinical guidelines require frequent updates due to research and technology advances. The quality of guideline updates can be improved if the knowledge underlying the guideline text is explicitly modelled using the so-called guideline patterns (GPs), mappings between a text fragment and a formal representation of its corresponding medical knowledge. Ontology-driven extraction of linguistic patterns is a method to automatically reconstruct the control knowledge captured in guidelines, which facilitates a more effective modelling and authoring of clinical guidelines. We illustrate by examples the use of a method for generating and searching for linguistic guideline patterns in the text of a guideline for treatment of breast cancer, and provide a general evaluation of usefulness of these patterns in the modelling of the guideline analyzed.