CCODERS OFTEN RELY on a neoplasm’s behavior and location for ICD-10-CM code assignment, rather than first referencing histological type. This oversight can lead to the coding error of inappropriately defaulting to the Neoplasm Table, resulting in a lack of specificity and incorrect code selection. When discussing neoplasms there are two basic groups: solid or- gan tumors, which originate in a single site or organ; and hemato- poietic and lymphatic malignancies, which originate in lymphatic, reticuloendothelial, or blood-forming tissues. 1 Although the cor- rect coding process is apparent for hematopoietic/lymphatic ma- lignancies, such as leukemia and lymphoma, when coding solid organ tumors histological designation may be overlooked in an inclination to highlight behavior and topography. This practice is
contradictory to the ICD-10-CM Official Guidelines for Coding and
Reporting issued by the Centers for Medicare and Medicaid Services (CMS), which direct coders to reference histological terms first.
Histology and Its Place in the Coding Process
Histology refers to the structure of cells, tissues, and organs in
relation to their functions. 2 The terms histology and morphology are typically used interchangeably in coding references. Both
terms are also found within notes on the Neoplasm Table. For the
purpose of this article the term “histology” will be used primarily
since it is the term used in Chapter 2 of the guidelines.
The histological type of a neoplasm may indicate the neoplasm’s
point of origin in the body and its behavior. Treatment decisions
are often individualized to a neoplasm’s histology (morphology).
Although histological type may indicate behavior, referencing
histology involves a distinct step in ICD-10-CM. The classifica-
tion includes four behavioral types—benign, in-situ, malignant,
or of uncertain behavior—in contrast to the numerous histology
descriptors found in the Alphabetic Index. Behavioral coding op-
tions may be located within the index or the table, while histologi-
cal descriptors are referenced exclusively through the index.
According to the Chapter 2 guidelines, neoplasm coding involves
three distinct steps. First, the histological term (if documented)
should be referenced to determine the appropriate column in the
Neoplasm Table. By referencing the histological term, the coder
may locate the appropriate code, if it is listed under the alphabetic
entry. If there is no direct coding instruction, the coder’s second
step is to follow the instructional notes to reference the appropriate
site and behavior column on the Neoplasm Table. Third, after locating the code in the table, the coder should reference the Tabular
List for final verification. Each step is vital to correct code selection.
If the histological term is not documented, the coder is directed to
go straight to the Neoplasm Table in lieu of accessing the Alphabetic Index.
Histology Impacts Code Choice
Histological (morphological) designation impacts code choice
in several ways. First, there are several ICD-10-CM codes that are
histology-specific. Basal cell carcinomas of the skin, GISTs, Leukemias, Lymphomas, Mesotheliomas, Merkel cell carcinomas, Melanomas, Neuroendocrines, and Squamous cell carcinomas of the
skin all have unique primary site codes indicating their histology.
Neuroendocrine tumors also have unique secondary (metastasis)
codes for carcinoid, Merkel cell, and other. If a solid organ tumor of
a specific histological type does not have a unique histological sec-
The Importance of Histology in
By Charlotte M. Bumgarner, CDIP, CCS, and Jennifer C. Latva, CCS, COC, CPC, CGSC