QC Corner Coding Tips
Coding Guidelines for Low Grade Appendiceal Mucinous Neoplasm LAMN Tumors of the Appendix (C18.1)
Determining Tumor Behavior and Code Assignment
LAMN tumors (ICD-O-3 code 8480) of the appendix can be classified based on the extent of tumor invasion. The behavior code is determined as follows:
• In Situ (Behavior Code 2): If the tumor is confined to the muscularis propria, it should be coded as in situ.
• Malignant (Behavior Code 3): If the tumor extends beyond the muscularis propria, it should be coded as malignant.
Local Extension and SEER Summary Stage Coding
In LAMN tumors, local extension includes invasion into the subserosa. When assigning the summary stage:
Use Code 1 (Localized) if the only available statement is "Tumor invades through the muscularis propria into subserosa or mesoappendix but does not extend to the serosal surface," and there is insufficient information to distinguish between subserosa and mesoappendix involvement.
AJCC Staging Information
For tumors meeting the above criteria, the AJCC stage should be assigned as cTis N0 M0.
T1 and T2 do not apply to LAMN: acellular mucin or mucinous epithelium that extends into the subserosa or serosa should be assigned as T3 or T4a.
Ensuring Accurate Site-Morphology Coding
Tip: When confronted with an unlikely site-morphology combination edit during cancer case abstraction, first verify the primary site. Subsequently, conduct a thorough review of the medical record for alternative site-morphology combinations. If still unclear, refer to established resources, such as the Solid Tumor Rules or the Hematopoietic Database, and use CPC*Search to identify similar histology codes by tumor site. If ambiguity persists, consult the SEER Inquiry System (SINQ) or seek guidance from Ask A SEER Registrar. For biologically unlikely combinations that remain unresolved, employ a manual override using the appropriate codes, ensuring alignment with the latest Cancer PathCHART database for validation and adherence to current standards. Always verify the primary is coded correctly, reference resources, and apply manual overrides when necessary.
CPC Expert pathologists review changes to histology codes for the validity of site-histology combinations, whether it's valid, impossible, or unlikely. Registrars should remain vigilant with updates to coding standards and validation lists, as these resources are frequently revised to reflect advancements in cancer classification and surveillance. Staying current with the Cancer PathCHART database and associated coding references not only improves data accuracy but also supports consistency across cancer registries. Registrars contribute to the reliability of cancer data, facilitating research, patient care, and public health initiatives.
Do Not Use Ambiguous Terms to Code LVI
Only assign a positive code for lymph vascular invasion (LVI) when the pathology report or a physician’s statement clearly documents the presence of LVI or its synonyms (such as angiolymphatic invasion, blood vessel invasion, lymphatic invasion, or vascular invasion).
Do not code LVI as present if the pathology report uses ambiguous language (e.g., “suspicious for LVI” or “foci suspicious for LVI”). In such cases, assign code 9 to indicate uncertainty or insufficient information.
Assign code 9 if there is no microscopic examination of the primary specimen, the sample is cytology only or a fine needle aspiration, or if the specimen is too small or insufficient to determine LVI status.
LVI is not mentioned in the pathology report, or information is missing from all available sources, code 9 should also be used.
Always refer to the SEER Program Coding and Staging Manual or STORE Standards for Oncology Registry Entry for guidance on coding LVI and ensure transparent and explicit documentation before assigning a definitive code.
Reference all coding resources when coding site-morphology, lymph vascular invasion, and behavior for LAMN tumors.
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