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SEER Inquiry System - Report
Produced: 01/08/2026 12:34 PM
Question 20021124
Inquiry Details
References:
SEER Program Code Man, 3rd Ed, 12
Question:
Multiple Primaries (Pre-2007)/Primary Site/EOD-Extension--Lung: Should lung cases be counted as more than one primary when nodules removed from separate lobes of the same lung have either the same histology or they are different immunophenotypes of the same main histologic classification (e.g., adenocarcinoma)? See discussion.
Discussion:
1. Path report: "Two nodules (RLL, RUL) of primary pulmonary demonstrate adenocarcinoma with different histologic appearances and different immunophenotypes consistent with synchronous lung adenocarcinomas." Per ICC interpretation, two lung primaries are favored.
2. Path report: "Two peripheral nodules (LLL, LUL) demonstrate similar P.D. non-small cell carcinoma with features of large cell undifferentiated carcinoma."
Answer:
For tumors diagnosed prior to 2007:
According to current SEER rules, both examples represent one primary because both tumors are in one lung and of a single histologic type. Code the Primary Site field to C34.9 [Lung, NOS] for both examples and the EOD-Extension field to 77 [Separate tumor nodules in different lobe]. This will capture the fact that there are multiple tumors within the lung for each of these examples.
Differences in immunophenotypes confirm independent de novo cancers and rule out metastasis. Immunophenotype differences do not equate to different histologies. In the first example described, there are different histologic features; however, the main classification is adenocarcinoma.
For tumors diagnosed 2007 or later, refer to the MP/H rules. If there are still questions about how this type of tumor should be coded, submit a new question to SINQ and include the difficulties you are encountering in applying the MP/H rules.
