Information about cancer stage in a patient is crucial when clinicians assess treatment progress. Determining cancer stage is a process that takes into account the description, location, characteristics and possible metastasis of cancerous tumors in a patient. It should follow classification standards, such as TNM Classification of Malignant Tumors. However, in clinical practice, the implementation of this process can be tedious and error-prone and create uncertainty. In order to alleviate these problems, we intend to assist radiologists by providing a second opinion in the evaluation of cancer stage in patients. For doing this, Semantic Web technologies, such as ontologies and reasoning, will be used to automatically classify cancer stages. This classification will use semantic annotations, made by radiologists (using the ePAD tool) and stored in the AIM format, and rules of an ontology representing the TNM standard. The whole process will be validated through a proof of concept with users from the Radiology Dept. of the Stanford University.