Collaborative Stage

Note 2: When a patient has more than one area of 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 10, 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 10, 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	TNM 7 Map	TNM 6 Map	SS77 Map	SS2000 Map
00	No distant metastasis	M0	NA	NONE	NONE
10	Distant lymph node(s): Celiac lymph node(s) Distant lymph node(s), NOS	M1	NA	D	D
11	For jejunum and ileum primaries only: Pericholedochal (For duodenal primary, see CS Lymph Nodes field)	M1	NA	D	RN
40	Distant metastases except distant lymph node(s) Carcinomatosis	M1	NA	D	D
50	40 + (10and/or 11) Distant metastasis plus distant lymph node(s)	M1	NA	D	D
60	Distant metastasis, NOS Stated as M1 with no other information on distant metastasis	M1	NA	D	D
99	Unknown; distant metastasis not stated Distant metastasis cannot be assessed Not documented in patient record	M0	NA	U	U

GISTSmallIntestine

CS Mets at DX