Gastrointestinal stromal tumor of large intestine

This code identifies a malignant or potentially malignant mesenchymal tumor originating from the interstitial cells of Cajal, specifically located within the large intestine. These tumors are characterized by their unique histopathology and often express KIT (CD117) protein.

Assign this code when documentation confirms a diagnosis of a gastrointestinal stromal tumor (GIST) explicitly localized to the large intestine. This includes findings from pathology reports, operative notes, or imaging studies detailing the tumor's origin in the colon or rectum.

• Ensure the documentation clearly specifies the large intestine as the primary site; GISTs can occur throughout the GI tract.
• Do not confuse with other gastrointestinal neoplasms like adenocarcinoma or lymphoma; GISTs have distinct histological features.
• Code the specific behavior (e.g., malignant, uncertain) if further specified in the pathology report, using more specific codes within the C49.A- series.