What is the primary concern with 'in situ' cancers if left untreated?

The primary concern with 'in situ' cancers, which refer to cancerous cells that are localized and have not yet invaded surrounding tissues, is that they may become invasive if left untreated. 'In situ' indicates that the cancer is contained within the tissue of origin, which could potentially develop into a more advanced and aggressive form if given enough time. If these early-stage cancers are not addressed, the risk increases for them to break through the local barriers and spread to nearby tissues or metastasize to other parts of the body. This progression underscores the importance of monitoring and treating 'in situ' cancers promptly to prevent escalation into invasive cancer, which would complicate treatment and reduce the likelihood of a favorable outcome.

The other options either incorrectly outline the nature of 'in situ' cancers or misrepresent the situation. For instance, describing them as purely benign ignores their potential for growth and invasion, while stating that they have a high cure rate does not address the risk of progression if treatment is delayed. Additionally, the assertion that they disappear over time is misleading, as untreated cancers typically require intervention rather than resolving spontaneously. Recognizing the potential for invasiveness highlights why timely treatment is crucial.