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SEER Inquiry System - Report
Produced: 05/04/2026 3:05 AM
Question 20230043
Inquiry Details
References:
#1: Solid Tumor Rules. Lung, May 2023 Update
#2: ICD-O-3.2
Question:
Solid Tumor Rules/Histology--Lung: What is the histology code for a lung tumor diagnosed as “Minimally invasive adenocarcinoma, mixed mucinous and non-mucinous, grade 1, lepidic-predominant”? See Discussion.
Discussion:
The resection pathology report final diagnosis indicates this is both mixed mucinous and non-mucinous with a lepidic predominant component. The pathologist notes this is “Lepidic: 75%. Acinar: 25%.” The percentage of the mucinous component is not documented.
Rule H1, Note 1, states “When mucinous carcinoma is mixed with another histology, such as adenocarcinoma and mucinous carcinoma, code mucinous ONLY when mucinous is documented to be greater than 50% of the tumor.” While mixed invasive mucinous and non-mucinous carcinoma is included in Table 2 (Combination/Mixed Histology Codes) without a required percentage, it is unclear whether one should move past Rule H7 and use Rule H8 to code this combination histology code. Rule H7 would instruct one to code the histology to lepidic adenocarcinoma (adenocarcinoma, lepidic predominant) based on the percentage of the lepidic component in the tumor. However, this does not address the mixed mucinous and non-mucinous diagnosis. Which H Rule and histology apply to this case?
Answer:
Assign histology code 8254/3 (mixed invasive mucinous and non-mucinous adenocarcinoma) to this lung tumor using Lung Solid Tumor Rules, Rule H4. This is a new code/term approved by IARC/WHO for ICD-O. Rule H4 instructs one to code the histology when only one histology is present. In this case, the pathologist indicates the tumor is mixed mucinous and non-mucinous histologies. The non-mucinous carcinoma that is seen in this mixed histology may be identified as: Adenocarcinoma in situ, minimally invasive adenocarcinoma, or lepidic predominant adenocarcinoma. In this case it is lepidic predominant adenocarcinoma. Lepidic is a recognized histology in lung. It is not unusual for the pathologist to indicate mixed non-muncinous and mucinous adenocarcinoma AND also list the non-mucinous subytpe. It is important to capture both mucinous and non-mucinous histologies which drives treatment, etc.
