Which statement about the sequence number field is true for a patient with one reportable malignant primary?

The sequence number field is crucial for tracking the timeline of tumor diagnoses in cancer registries. For a patient with only one reportable malignant primary tumor, the sequence number is standardized to be recorded as 00. This indicates that there is no previous malignancy in the patient's history, defining that this is the first and only diagnosis.

As for the other choices, the tumor sequence number typically does not change over time if only one malignant primary is recorded; hence, option B is not valid. This field is specifically for malignancies, making option C inaccurate since it does not pertain to benign tumors. Lastly, since the sequence number is primarily for tracking the occurrence of malignancies, it does indeed relate to staging by providing context for prior diagnoses, indicating that option D is also incorrect. Thus, the statement that accurately reflects the characteristics of the sequence number field for a single reportable malignant primary is that it will always be recorded as 00.