#1: Update to current manual
#2: Solid Tumor Rules (2018)
Source 1: 2018 Solid Tumor Rules
Notes: Lung, January 2019 update
Source 2: Subject matter expert
Update to current manual/Solid Tumor Rules (2018)/Histology--Lung: What is the histology code and what M Rule applies when there are multiple specific subtypes identified using various equivalent lung terms but only one is stated to be predominant? See Discussion.
Example: Lung resection final diagnosis is Lung adenocarcinoma, see Summary Cancer Data, and the Summary Cancer Data (CAP Synoptic Report) states Histologic type: Invasive adenocarcinoma, solid predominant. Other Subtypes Present: 20% acinar and <5% micropapillary components.
Instruction 1B and Note 1 for Coding Multiple Histologies (Lung Histology Rules) indicates type, subtype, component, and predominantly are all terms that may be used to code the most specific histology. In this case, the multiple specific histologies were documented using all of those terms.
Note 2 for instruction 1B states predominantly describes the greatest amount of tumor and when it is used for the listed subtypes of adenocarcinoma, that subtype should be coded. However, Note 2 does not indicate that the other subtypes are ignored when one is identified to be predominant and the others are identified as subtype or component only.
Code to invasive adenocarcinoma, solid predominant (8230/3), based on the example, using Lung Solid Tumor Rules Coding Multiple Histologies instruction #1 that says to code the specific histology where the most specific histology may be described as component, majority/majority of, or predominantly, in this case, 75%. Apply Rule M2 as this appears to be a single tumor with multiple histologies based on the information provided.
The rules will be updated to add a new H rule and to reviseTable 2 when two or more histologies described as predominant are present.