Sources to Use to Determine Primary Site (Unless Otherwise Specified in Site-Specific Instructions)

The site of origin should be classified according to the medical opinion on the case. Information about a tumor’s site of origin can be found in several places in the medical record.


  • Imaging reports
  • History and physicals
  • Operative reports
  • Pathology reports
  • Tumor board documentation

In most cases, all available information should be used to determine the primary site. For some sites, a priority order has been established. For example, when the medical record contains conflicting information about the specific site of origin for a colon primary, use the following priority order.

  • Resected cases
    • Operative report with surgeon’s description
    • Pathology report
    • Imaging
  • Polypectomy or excision without resection
    • Endoscopy report
    • Pathology report

Using these instructions for a colon cancer case that has undergone a surgical resection, the operative report with surgeon’s description has the highest priority for determining the primary site. If the medical records for such a case described the primary site as sigmoid colon in the imaging report and as descending colon in the operative report, preference would be given to the operative report and the code for descending colon would be assigned. Refer to the SEER Coding Guidelines for Colon in Appendix C of the SEER Program Coding and Staging Manual for these instructions.

It is important for a cancer registrar to be familiar with the procedures that assist physicians in diagnosing a malignancy.

The presence of a possible malignancy may be first detected during the initial physician clinical examination. During the physical examination, the physician will closely observe all external surfaces and palpate various portions of the body. The physician will record his/her findings relative to the various body regions including where he/she believes may be a primary area of concern. Further diagnostic tests and procedures may be ordered to confirm a clinical impression, distinguish one disease from among several possibilities, identify more precisely the extent of the disease, and determine a patient's overall state of health. Additional reports may be found in the following sections of a medical record:

  • Laboratory (blood and urine)
  • Operative/Surgical
  • Radiology
  • Endoscopy
  • Pathology/Cytology

A final report from each diagnostic procedure will be added to the patient’s medical record. The procedure reports contain crucial information to assist the registrar in documenting the diagnosis of cancer as well as the physician’s impression of the malignancy and extent of disease.

For more information on these diagnostic procedures, see the Abstracting a Cancer Case section of the SEER Training Website.

A tumor board is a group of doctors and other health care providers with different specialties that meets regularly at the hospital to discuss cancer cases and share knowledge. The board’s goal is to determine the best possible cancer treatment and care plan for an individual patient. Tumor board meetings can include doctors such as pathologists, surgeons, and medical and radiation oncologists. Depending on the cases being discussed, additional doctors, such as gynecologists, plastic surgeons, or urologists, may also participate. Specialists such as radiologists and pathologists also attend to help provide advice and perspectives on a cancer diagnosis. A diverse range of other health care providers, including nurse specialists and social workers, may take part as well.  Discussions during this review are documented and can also be vital to helping a registrar determine a tumor’s primary site of origin. Website Policy

Updated: December 13, 2023