The sequence number indicates the sequence of all reportable neoplasms over the lifetime of the patient and it is recorded in the sequence number data field.

Malignant and in situ neoplasms, including malignant CNS neoplasms, are assigned codes 00 through 35. If a patient has only one primary malignant or in situ neoplasm, the sequence number assigned is 00. If a patient has multiple primary neoplasms during a lifetime, the sequence number for the first tumor is 01, the sequence number for the second primary tumor is 02, and so forth.

Non-malignant tumors are coded in the 60 to 87 range. First non-malignant tumor will be coded 60. If a subsequent non-malignant tumor arises, it would be coded as 62 and the first non-malignant tumor changed to 61.

If a patient was diagnosed with a non-malignant CNS neoplasm before reporting was required (January 1, 2004 and earlier) and is diagnosed with a second non-malignant CNS neoplasm in 2004, the first neoplasm is assigned sequence number 61 and the second neoplasm is assigned sequence number 62 even though an abstract is required only for the second neoplasm.

When a non-malignant CNS tumor progresses into a malignant CNS tumor, sequencing of non-malignant does not affect sequencing of malignant. For example, if a patient had a non-malignant CNS tumor that progressed into a malignant CNS tumor, the sequence number for the benign tumor is 60, and the sequence number for the malignant tumor is 00.