Collaborative Stage

Note: When a patient has more than one area of gastrointestinal stromal tumor (GIST), it is important to try to distinguish between intra-abdominal metastasis and tumor multiplicity. Distant metastases are relatively rare in GISTs, but they are increasingly detected with sophisticated radiological studies. Intra-abdominal metastasis will present as tumor involvement in the abdominal cavity outside the main tumor mass, in the peritoneum, omentum, serosae of organs, and the cul-de-sac, among other areas. Code this form of metastasis in CS Mets at DX.

Tumor multiplicity, in contrast, will present with anatomically separate, multiple tumors of different sizes arising independently in the GI tract. This form of tumor multiplicity usually will be seen in patients with neurofibromatosis type 1 or familial GIST syndrome, but in rare instances may be seen in patients without these conditions. This form of multiplicity should not be coded as metastasis, but the presence of multiple tumors should be coded in CS Site-Specific Factor 15, Tumor Multiplicity.

When a solitary omental or mesenteric tumor mass is found with a primary GIST elsewhere, do not code this as a metastasis. Code it as multiple tumors in CS Site-Specific Factor 15, Tumor Multiplicity.

When multiple tumor areas are present and it is not stated whether these are metastases or independent tumors, consult with a physician if possible to determine how to code them. If a decision cannot be made, code this site-specific factor as 010 (Multiple GIST tumors are present).

Code	Description
000	Multiple gastrointestinal stromal tumors (GIST) not present in the surgical specimen; single GIST; unifocal GIST
010	Multiple GIST tumors present in the surgical specimen; multifocal GIST
988	Not applicable: Information not collected for this case (If this information is required by your standard setter, use of code 988 may result in an edit error.)
999	Unknown if one tumor or multiple tumors No information on tumor multiplicity Not documented in patient record

GISTColon

CS Site-Specific Factor 15
Tumor Multiplicity

GISTColon

CS Site-Specific Factor 15Tumor Multiplicity

CS Site-Specific Factor 15
Tumor Multiplicity