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Question: What is the correct code for leiomyosarcoma (LMS) of the sigmoid colon? I have found documentation stating if the LMS 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.

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Answer: Your provider is correct, in this case.

Here鈥檚 why: According to the , LMS is 鈥渁 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 鈥� blood vessels 鈥� [and] the uterus.鈥�

This makes LMS a soft, or connective, tissue sarcoma. Per the ICD-10-CM Alphabetic Index, LMS is coded to Neoplasm, connective tissue, malignant, which is consistent with the note in the neoplasm table that tells you to code neoplasms of connective tissue according to 鈥楴eoplasm, connective tissue鈥� and to 鈥渃ode to neoplasm of that site鈥� for 鈥渟ites that do not appear in this list.鈥�

Because 鈥淣eoplasm, connective tissue, intestinal, malignant鈥� appears on the list for code C49.4 (Malignant neoplasm of connective and soft tissue of abdomen), that is the code you should use rather than coding the neoplasm to the site, which would be C18.7 (Malignant neoplasm of sigmoid colon).