What is the purpose of an accession number in a cancer registry?

The purpose of an accession number in a cancer registry is to serve as a unique identifier for each case as it is entered into the registry. This number is crucial because it allows for efficient tracking, retrieval, and management of data related to specific cancer cases throughout the registry's lifespan. Each accession number ensures that no two cases are confused with one another, even if they occur in the same patient or during the same time period. This unique identification is vital for the accurate analysis and reporting of cancer data, which supports epidemiological research, treatment studies, and public health initiatives.

While the other options may refer to various aspects of cancer data management, they do not accurately describe the specific function of an accession number. Thus, the correct choice directly relates to the number's role in identifying individual cases within the registry.