C49.A5

Billable

Gastrointestinal stromal tumor of rectum

HCC Category Mapping

V28HCC 23 — Melanoma and Other Skin Cancers

0.251

V24HCC 10 — Lymphoma and Other Cancers

0.675

ESRDHCC 10 — Lymphoma and Other Cancers

0.000

RxHCCHCC 20 — Cancer, Liver and Intrahepatic Bile Duct

0.000

What This Code Means

A gastrointestinal stromal tumor that occurs in the rectum, the final segment of the large intestine before the anus.

Coding Tips

•Verify the tumor is in the rectum and not in the sigmoid colon or anal canal
•Note any involvement of surrounding structures for staging and treatment planning documentation

Clinical Significance

Gastrointestinal stromal tumor of the rectum is an uncommon GIST location (approximately 5% of cases) with unique surgical considerations. Rectal GISTs often require neoadjuvant imatinib to shrink the tumor and enable sphincter-preserving surgery, making accurate diagnosis and coding critical for treatment authorization.

Documentation Requirements

✓Pathology confirming rectal GIST with immunohistochemistry
✓Tumor location relative to the anal verge and sphincter complex
✓Tumor size and mitotic rate
✓Endorectal ultrasound or MRI findings showing relationship to rectal wall layers
✓Treatment plan including neoadjuvant therapy consideration

Commonly Confused Codes

C20 (Malignant neoplasm of rectum) — rectal adenocarcinoma, not GIST C49.A4 (GIST of large intestine) — colonic GIST, not rectal C49.A0 (GIST, unspecified site) — use C49.A5 when rectum is documented C21._ (Malignant neoplasm of anus) — anal canal malignancy, not rectal GIST

Code Hierarchy

└C49Malignant neoplasm of other connective and soft tissue └C49.AGastrointestinal stromal tumor └C49.A5Gastrointestinal stromal tumor of rectum

└C49.A5Gastrointestinal stromal tumor of rectum