Topographic Regions and Ill-defined Sites

Rule A. If the diagnosis does not specify the tissue of origin, code the appropriate tissues suggested in the alphabetic index for each ill-defined site in preference to the "NOS" category.

The coding of diagnoses referring to regions and ill-defined sites of the body presents problems. Most ill-defined sites are listed under C76 in ICD-O but some, such as "arm," have several component tissues (Table 16). The diagnostic statement may not indicate the tissue in which the tumor originated. For example, "arm" may refer to "skin of arm," to various "soft tissues of the arm," or even to the "bones of the arm." "Arm, NOS," meaning that nothing more specific is known about the primary site, is coded to C76.4. To facilitate coding of tumors of the arm, specific tissues are listed below the term "arm" in the alphabetic index.

In the alphabetic index, examples of common benign or malignant neoplasms have been listed in parentheses and assigned to the specific tissue from which they usually arise. Carcinoma, melanoma, and nevus of the arm are coded to C44.6, the topography code that includes "skin of arm." These parenthetical notes are intended to assist the coder and to indicate, for example, that various types of carcinomas of the arm, such as squamous cell carcinoma or epidermoid carcinoma, should be coded to C44.6 (skin of arm) rather than C76.4 (arm, NOS).

Similarly, sarcoma and lipoma are coded to C49.1, the topography code for various soft tissues of the arm. Most sarcomas, such as fibrosarcoma, liposarcoma, and angiosarcoma, usually originate in soft tissue.

An approach similar to that outlined for arm was followed in the alphabetic index for other ill-defined sites and regions of the body which are listed under topography code numbers C76. Some ill-defined sites such as chin, NOS and forehead, NOS are not assigned to C76 but to skin (C44).

Particular care is needed for bone tumors. Both osteosarcoma (osteo meaning bone) and chondrosarcoma (chondro meaning cartilage) usually arise in bone. "Bone of arm" is coded to C40.0, which designates "long bones of upper limb, scapula and associated joints," and is the correct code number if the osteosarcoma or chondrosarcoma arises in one of the bones of the arm.

Peripheral Nerves and Connective Tissues

Peripheral nerves (C47._) and connective tissue (C49._) include a variety of tissues. Not all of these terms are included in the alphabetic index for all regions of the body. For example, adipose tissue is included with connective tissue but is not listed for every ill-defined site.