Total Field Length: 8 (YYYYMMDD Format)
Day (DD): 2 digit
Month (MM): 2 digit
Year (YYYY): 4 digit
The date of diagnosis is the month, day, and year the reportable neoplasm was first identified, clinically or
microscopically, by a recognized medical practitioner
Date of Diagnosis (DiagDate)
Date of Diagnosis
Enter the month, day, and year of the initial diagnosis (YYYYMMDD format)
- Code the date using a zero to precede single digit days, or months, i.e., June is entered as 06
This field refers to the date of first diagnosis of this cancer by a recognized medical practitioner. This is the date of the first clinical diagnosis, and in some cases, the diagnosis may never be histologically confirmed. Do not change the date of diagnosis when a later biopsy or cytology provides confirmation of a clinical diagnosis. From 2009 forward, for cases which are diagnosed in utero, record the actual date of diagnosis. For pre-2009 cases, the date of diagnosis for in utero cases should be the date of birth.
1. Code the month, day and year the tumor was first diagnosed, clinically or microscopically, by a
recognized medical practitioner
a. When the first diagnosis includes reportable ambiguous terminology, record the date of
Note: The date of the suspicious cytology may be used as the date of diagnosis when a definitive diagnosis follows the suspicious cytology for cases beginning 01/01/2022 forward. Do not use ambiguous cytology alone for case ascertainment.
2. When the only information available is a positive pathology or cytology report, code the date
the biopsy was done, not the date the report was dictated or transcribed
3. Code the date the procedure was done, not the date the specimen was received or read as
positive by the pathologist when the date of diagnosis is coded from a pathology report
4. The first diagnosis of cancer may be clinical (i.e., based on clinical findings or physician’s
Note: Do not change the date of diagnosis when a clinical diagnosis is subsequently confirmed
by positive histology or cytology.
Note: Appendix E in the 2023 SEER Program Manual lists which PI-RADS, BI-RADS,
and LI-RADS are reportable versus non-reportable. If reportable, use the date of the
imaging procedure as the date of diagnosis when this is the earliest date and there is no
information to dispute the imaging findings.
5. Positive tumor markers alone are not diagnostic of cancer. Use the date of clinical, histologic,
or positive cytologic confirmation as the date of diagnosis.
Note: Positive tumor markers alone are never used for case ascertainment.
6. Use the date of suspicious cytology when the diagnosis is proven by subsequent biopsy,
excision, or other means
Note 1: “Suspicious” cytology means that the diagnosis is preceded by an ambiguous term such
as apparently, appears, compatible with, etc.
Note 2: Do not use ambiguous cytology alone for case ascertainment.
7. Code the earlier date as the date of diagnosis when
a. A recognized medical practitioner says that, in retrospect, the patient had cancer at an
earlier date or
b. The original slides are reviewed and the pathologist documents that cancer was present.
Code the date of the original procedure as the diagnosis date.
Note: Do not back-date the diagnosis when
• The information on the previous tumor is unclear AND/OR
• There is no review of previous slides AND/OR
• There is no physician’s statement that, in retrospect, the previous tumor was malignant
8. Code the date of death as the date of diagnosis for autopsy only cases
9. Death certificate only (DCO) Cases
a. Use information on the death certificate to estimate the date of diagnosis
b. Record the date of death as the date of diagnosis when there is not enough information
available to estimate the date of diagnosis; for example, the time from onset to the date of
death is described as ‘years’
c. If no information is available, record the date of death as the date of diagnosis
10. Estimate the date of diagnosis if an exact date is not available. Use all information available to
calculate the month and year of diagnosis.
a. Estimating the month
i. Code “spring” to April
ii. Code “summer” or “middle of the year” to July
iii. Code “fall” or “autumn” as October
iv. For “winter” try to determine whether the physician means the first of the year or
the end of the year and code January or December as appropriate. If no
determination can be made, use whatever information is available to calculate the
month of diagnosis.
v. Code “early in year” to January
vi. Code “late in year” to December
vii. Use whatever information is available to calculate the month of diagnosis
viii. Code the month of admission when there is no basis for estimation
ix. Leave month blank (or convert 99 to blank) if there is no basis for approximation
b. Estimating the year
i. Code “a couple of years” to two years earlier
ii. Code “a few years” to three years earlier
iii. Use whatever information is available to calculate the year of diagnosis
iv. Code the year of admission when there is no basis for estimation
11. If no information about the date of diagnosis is available
a. Case transmitted to NCI SEER
i. Use the date of admission as the date of diagnosis
ii. In the absence of an admission date, code the date of first treatment as the date of
b. Case NOT transmitted to NCI SEER
i. Code month and year as unknown
Nursing Home and Hospice Residents (Not hospitalized for their cancer; no information other
than nursing home or hospice records and/or death certificate)
1. Use the best approximation for the date of diagnosis when the only information available is
that the patient had cancer while in the nursing home and it is unknown whether the patient
had cancer when admitted
2. Code the date of admission to the nursing home as the date of diagnosis when
a. The only information available is that the patient had cancer when admitted to the
b. The only information available is that the patient had cancer while in the nursing home,
it is unknown whether the patient had cancer when admitted, and there is no basis for
Cases Diagnosed Before Birth
Record the actual date of diagnosis for diagnoses made in utero even though this date will precede the date of
Note: Prenatal diagnoses are reportable when there is a live birth.
The date of death is the date of diagnosis for a class of case 38.
See SEER Manual (pages 83-87) for Examples