Pathology/Lab Coding Alert

Question: What is the correct code for leiomyosarcoma of the sigmoid colon? I have found documentation stating if the leiomyo­sarcoma has originated in an organ, then it should be coded to the site. However, the provider is insisting that it should be coded to connective tissue.

AAPC Forum Participant

Answer: Your provider is correct, in this case.

Here’s why: According to the National Cancer Institute, leiomyosarcoma (LMS) is “a type of rare cancer that grows in the smooth muscles. The smooth muscles are in the hollow organs of the body, including the intestines, stomach, bladder … blood vessels … [and] the uterus” (www.cancer.gov/ pediatric-adult-rare-tumor/rare-tumors/rare-soft-tissue-tumors/ leiomyosarcoma).

This makes LMS a soft, or connective, tissue sarcoma. The ICD-10-CM Alphabetic Index entry for LMS directs you to find your code under Neoplasm, connective tissue, malignant.

The “Neoplasm, connective tissue” entry in the neoplasm table includes the subentry “intestinal,” and the column for “Malignant, Primary” points you to C49.4 (Malignant neoplasm of connective and soft tissue of abdomen). That means you should report this case using C49.4 rather than coding the neoplasm to the site, which would be C18.7 (Malignant neoplasm of sigmoid colon).