#2: Primary site
Source 1: 2018 SEER Manual
pgs: 7, 90
Source 2: 2018 Solid Tumor Rules
Notes: Colon, January 2019 Update
Reportability/Primary Site--Gastrointestinal (GI) Tract: Is a gastrointestinal stromal tumor (GIST) with a single nodule in the small intestine (C17_) and a nodule in the stomach (C16_) reportable per the 2018 SEER Coding Manual reporting instructions for GIST due to the multiple foci or do the multiple foci need to be in the same organ to be reportable? See Discussion.
Example: Small intestine wedge resection with GIST, 1.8 cm in mid small intestine, single nodule. Stomach nodule biopsy: GIST, 0.3 cm. Pathology report comment section indicates the gastric GIST is not staged due to the small size and incidental nature.
Report the GIST in the small intestine. The 2018 SEER Manual says to report GIST when there are multiple foci and to code the primary site to the site where the malignancy originated. Use text fields to record the details, including the stomach nodule.