Pathology/Lab Coding Alert

Know ‘sarcoma’ behavior.

The short answer to this coding quiz is: C49.A3 (Gastrointestinal stromal tumor of small intestine).

Follow Expert Guidance to Assign GIST Dx

To find the proper diagnosis code for a gastrointestinal stromal tumor (GIST), start in the ICD-10-CM index by looking up “tumor,” says Kelly C. Loya, CPC-I, CHC, CPhT, CRMA, Associate Partner, Pinnacle Enterprise Risk Consulting Services, LLC. Under “tumor,” locate the term “stromal” and then underneath find “gastrointestinal,” says Loya.

The index then points you to different codes based on the information available in the documentation.

If GIST is the only information you have, the default code is C49.A0 (Gastrointestinal stromal tumor, unspecified site). But in this case, you know the site is small intestine, so C49.A3 is the better choice. ICD-10 CM provides other options in this code family for GISTs of other sites, as follows:

• C49.A1 (Gastrointestinal stromal tumor of esophagus)
• C49.A2 (Gastrointestinal stromal tumor of stomach)
• C49.A4 (Gastrointestinal stromal tumor of large intestine)
• C49.A5 (Gastrointestinal stromal tumor of rectum)
• C49.A9 (Gastrointestinal stromal tumor of other sites)

Double Check Behavior to Ensure Proper Code

Sometimes the pathology report will point to a GIST tumor, but specify that the cellular changes are of “uncertain behavior” or “benign.

Uncertain behavior: If the documentation specifies uncertain behavior, you should not use a C49.A- code, but instead turn to code D48.1 (Neoplasm of uncertain behavior of connective and other soft tissue). In fact, a note with D48.1 specifies that the code is appropriate for stromal tumors of the digestive system.

Benign: If the documentation indicates a benign stromal tumor, you should turn to D21.4 (Benign neoplasm of connective and other soft tissue of abdomen).

Understand sarcoma: In this case, the pathology report assigns a final narrative diagnosis of gastrointestinal stromal sarcoma. Because sarcoma is, by definition, a malignant neoplasm, you know that the correct code for this case is the malignant GIST code for small intestine, C49.A3.

Don’t Let the “A” Confuse You

Most coders learned that ICD-10-CM codes have a first character that is alpha, but that the second, third, and fourth characters are always numeric.

Although that was initially true during the implementation year of ICD-10-CM, the addition of codes over the years has sometimes required using alpha second, third, or fourth characters. But if C49.A- leaves you scratching your head, here’s what you need to know:

ICD-10-CM contains specific codes for most C49.- fourth-digits 1-9. You’ll find C49.A following code C49.9.