Site-Associated Morphology Terms

Rule H. Use the topography code provided when a topographic site is not stated in the diagnosis. This topography code should be disregarded if the tumor is known to arise at another site.

Some terms for neoplasms imply origin in certain sites or types of tissue. Examples are shown in the table below. To facilitate the coding of such terms, a topography code has been added in parentheses in both the numeric list of morphology and the alphabetic index, when appropriate. Occasionally the topography code appears in the 3-digit heading and the then applies to all terms included under that heading.

For "basal cell carcinoma" (Table 23), the topography code for skin (C44._) is given, with the fourth digit left open. An underscore (_) following the decimal point indicates the existence of subsite codes. The appropriate fourth digit for the site reported should be added here. Coders should refer to the numerical list or the alphabetic index for specific subsite codes. For example, a basal cell carcinoma of the face would be given the site code C44.3 (skin of face), while one of the arm would be coded C44.6 (skin of arm). Similarly the fourth digit in the topography code (C70._) that follows "meningioma" is left open since the site involved may be either "cerebral meninges" (C70.0), "spinal meninges" (C70.1), or "meninges, NOS" (C70.9).

The topography code attached to a morphology term may be used when the topographic site is not given in the diagnosis. Many morphology terms do not have topography codes assigned because the tumors frequently arise in more than one organ or topographic site. For example, "adenocarcinoma, NOS" has no assigned topography code because it can be primary in many different organs.

It may be that the site given in a diagnosis is different from the site indicated by the site-associated topography code. For example, basal cell carcinoma can arise in sites other than skin. When a different primary site is give, coders should ignore the topography code listed in ICD-O and use the appropriate code for the topography included in the diagnosis. For example, topography code C50._ (Breast) is added to the morphology term "infiltrating duct carcinoma," because this term is usually used for a type of carcinoma that arises in the breast. However, if the term "infiltrating duct carcinoma" is used for a primary carcinoma arising in the pancreas, coders should ignore the suggested breast topography code and assign the correct code, C25.9 (pancreas, NOS) instead.

Remember that the site-associated topography codes attached to morphology terms designate the usual site of origin of particular neoplasms. An unusual, but possible, example would be the diagnosis "osteosarcoma of kidney," for which the kidney topography code (C64.9) would be used instead of "bone, NOS" (C41.9) after the record has been thoroughly checked to ascertain that a bone cancer has not metastasized to the kidney. A bone cancer (osteosarcoma) metastasis to the kidney would be coded C41.9 (bone), M-9180/3 (osteosarcoma).

Pseudo-topographic Morphology Terms

Certain neoplasms have names that appear to be site-specific but these entities should not necessarily be coded to that site. For example, "bile duct carcinoma" (M-8160/3) is a specific histologic type, frequently found in both the intrahepatic bile ducts of the liver (C22.1) and in the extrahepatic bile ducts (C24.0), and therefore should not be automatically coded to C24.0.

Neoplasms of the minor salivary glands can be found anywhere in the oral cavity and neighboring organs and include several histologic types such as "adenoid cystic carcinoma," "malignant mixed tumor," and "adenocarcinoma, NOS." Hence there is no distinctive morphology code for "minor salivary gland carcinoma." Since all types of adenocarcinoma of the mouth or oral cavity are considered to be of minor salivary gland origin, the words "minor salivary gland" should be ignored in a diagnosis such as "minor salivary gland adenoid cystic carcinoma of the hard palate." In this example, the "adenoid cystic carcinoma" (M-8200/3) should be coded to the topographic site "hard palate" (C05.0). If not site of origin is given in a diagnosis, such as "minor salivary gland adenocarcinoma," coders should use the topography code for oral cavity, C06.9, which includes "minor salivary gland, NOS."