V.1 Primary Site

Coding Instructions:

• The ICD-O-3 (International Classification of Diseases for Oncology, Third Edition, 2000) must be used for coding primary site. This applies to cases diagnosed January 1, 2001 and forward.

• Identify the primary site by careful scrutiny of all reports in the patient's medical record.

• Where information in the record is conflicting, statements in the pathology report generally take precedence over other statements.

• If the record does not provide a clear answer, ask the patient's physician.

• If the only information available is the secondary site, then it should be reported in accordance with the instructions in Section Primary Site - Site Specific Special Conditions.

• The Primary Site field codes are found in the Topography section of the ICD-O-3 (International Classification of Diseases for Oncology, Third Edition, 2000). In the Index for the ICD-O-3, the site is indicated by a four character code. The first character is always a “C”, followed by three numbers.

• The first two numerical digits stand for the primary site (organ, tissue, or structure). The third digit identifies the subsite of the primary site.

• A computerized axial tomographic (CT or CAT) scan of a patient's chest revealed a large malignancy in the upper lobe of the left lung. The correct ICD-O-3 code is therefore C34.1, which should be entered C341.

• (2) The site cardia of the stomach (the part of the stomach at the opening of the esophagus) is listed in the Index for the ICD-O-3 under "cardia" or "stomach, cardia" as T-C16.0, which should be entered C160.

• Code the last digit of the primary site code to '8' when a single tumor overlaps an adjacent subsite(s) of an organ and the point of origin cannot be determined.

• Code a transplanted organ to the primary site the organ is grafted to.

• When the medical record does not contain enough information to assign a primary site:

• Code unknown primary in the absence of any information when the physician is not able to identify a primary site (see Q-Tips on Unknown Primary).

• Use the NOS code for the organ system or ill-defined site (C760-C768) when there are two or more possible primary sites documented and they are within the same system.

• Assign C148 when there is an unknown head and neck primary.

• In the absence of any additional information, assign the codes listed for these primary sites:

Codes:

For Primary Site coding rules:

See Section V.1.1 Identification of Separate Sites

See Section V.1.2 Indefinite and Metastatic Sites

See Section V.1.3 Primary site - Site Specific

See Section V.1.4 Uncertain Diagnosis

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