GISTPeritoneum - CS Mets at DX

Note 1: Liver metastasis implies the presence of tumor inside the liver parenchyma as one or more nodules. Adherence to the liver capsule, even if extensive, should not be considered distant metastasis. Code direct adherence to the liver in CS Extension code 600.
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 7, 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 7, 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 as 99

Code	Description	TNM 7 Map	TNM 6 Map	SS77 Map	SS2000 Map
00	No distant metastasis	M0	M0	NONE	NONE
10	Distant lymph node(s)	M1	M1	D	D
40	Distant metastasis except distant lymph node(s) (code 10) Distant metastasis, NOS Carcinomatosis	M1	M1	D	D
45	Distant metastasis except distaint lymph node(s) Carcinomatosis	M1	M1	D	D
50	(10) + (40) Distant lymph node(s) plus other distant metastases	M1	M1	D	D
60	Distant metastasis, NOS Stated as M1 with no other information on distant metastasis	M1	M1	D	D
99	Unknown; distant metastasis not stated Distant metastasis cannot be assessed Not documented in patient record	M0	MX	U	U