For a patient treated for colon cancer with a history of previous cancer, what would be the sequence number assigned for colon cancer?

In cancer registry coding, the sequence number signifies the order in which different primary cancers occur in a patient's medical history. Each distinct primary cancer is assigned a unique sequence number starting with 01 for the first primary cancer diagnosed.

Since the patient has a history of a previous cancer, the colon cancer diagnosis would be considered a subsequent primary malignancy. Thus, this patient's colon cancer would be assigned a sequence number of 02, which indicates that it is the second primary cancer documented in their medical history. This proper sequencing is crucial in oncology data management, as it helps in tracking treatment outcomes, statistical analysis, and research.

The assignment of 01 would erroneously denote that this cancer was the first primary, which it is not. Sequence numbers 03 and any higher numbers would not be applicable as there is only one previous cancer documented; therefore, they indicate an even later occurrence. A sequence number of 00 is typically used for non-malignant conditions or when the sequence is unknown, which is not relevant in this case where you are dealing with verified primary cancers.