Malignant neoplasm of isthmus uteri

This code signifies a primary cancerous tumor originating in the isthmus of the uterus, which is the narrow lower segment connecting the body of the uterus to the cervix. This malignancy is a type of uterine cancer specifically located in this transitional zone.

Assign this code when documentation clearly specifies a primary malignant neoplasm confined to or originating in the isthmus uteri. This is typically supported by pathology reports confirming malignancy and precise anatomical location, or by imaging studies and physician notes detailing the tumor's site.

• Differentiate carefully from malignancies of the corpus uteri (C54.1) or cervix uteri (C53.-).
• Ensure the documentation specifies "primary" malignancy; secondary or metastatic lesions would be coded differently.
• Always review the pathology report for definitive site and histology, as well as the physician's final diagnosis.