Pathology/Lab Coding Alert

Question: We have a pathology report that describes the colon tumor specimen as “gastrointestinal stromal sarcoma.” What is the correct diagnosis code for this case?

Oklahoma Subscriber

Answer: The correct code is C49.A4 (Gastrointestinal stromal tumor of large intestine).

Vocabulary is key: To crack this case, you need to know that a sarcoma is a malignant neoplasm, that “stromal” refers to connective tissue, and that the colon is synonymous with the large intestine.

ICD-10 CM provides a code family for gastrointestinal stromal tumors (GISTs) based on tumor site, as follows:

• C49.A0 (Gastrointestinal stromal tumor, unspecified site)
• C49.A1 (Gastrointestinal stromal tumor of esophagus)
• C49.A2 (Gastrointestinal stromal tumor of stomach)
• C49.A3 (Gastrointestinal stromal tumor of small intestine)
• C49.A4 (Gastrointestinal stromal tumor of large intestine)
• C49.A5 (Gastrointestinal stromal tumor of rectum)
• C49.A9 (Gastrointestinal stromal tumor of other sites)

Understand the “A”: You probably learned that ICD-10-CM codes have a first character that is alpha, but that the second, third, and fourth characters are always numeric.

That was true when the code set was implemented, but the addition of codes over the years has sometimes required using alpha second, third, or fourth characters.

Find it: ICD-10-CM contains specific codes for different sites in the family C49 (Malignant neoplasm of other connective and soft tissue), with fourth characters 1-9 that specify the site. You’ll find the C49.A (Gastrointestinal stromal tumor) group of codes following code C49.9.