What does this LOINC code represent?

This LOINC code identifies a lab observation, measurement, question, or clinical concept in a standardized format.

Is this enough to understand my test result?

No. The code identifies the test or observation, but the interpretation depends on the actual result, reference range, and clinical context.

LOINCActive

LOINC Code 21998-0: Ill defined site override flag Cancer case

Name: LOINC Code 21998-0: Ill defined site override flag Cancer case
Creator: HealthAssure Clinical Team
Published: 2026-05-21T11:17:30.108Z

21998-0 is a LOINC code used to identify Ill defined site override flag Cancer case in laboratory and clinical observation data. You may see this code in lab systems, lab reports, EHR exports, interoperability feeds, or other structured clinical data exchanges. LOINC codes identify tests, measurements, observations, survey items, and clinical questions in a standardized way. It is associated with the component Ill defined site override flag. It is commonly used with the system or sample type Cancer case.XXX.

Reviewed by HealthAssure Clinical TeamUpdated 21 May 2026

What is this code?

LOINC codes identify tests, measurements, observations, survey items, and clinical questions in a standardized way. It is associated with the component Ill defined site override flag. It is commonly used with the system or sample type Cancer case.XXX.

When is it used?

Used in lab systems, EHRs, and clinical data exchange.
May identify a test, observation, survey item, or clinical document request rather than a diagnosis.
Status: ACTIVE

What it does not mean

The code identifies the observation or test, not the actual result.

Key facts

Ill defined site override flag Cancer case

Ill defined site override flag

Some computer edits identify errors. Others indicate possible errors that require manual review for resolution. To eliminate the need to review the same cases repeatedly, over-ride flags have been developed to indicate that data in a record (or records) have been reviewed and, while unusual, are correct. This over-ride is used with the following edits in the NAACCR Metafile of the EDITS softwareSeq Num--Central, Primary Site, Morph (NAACCR IF22) Seq Num--Central, Primary Site, Morph (SEER IF22) Seq Num--Central, Prim Site, Morph ICDO3 (NAACCR IF22) Seq Num--Central, Prim Site, Morph ICDO3 (SEER IF22) Some edits check for code combinations that are possible, but quite rare. If the code combination generates an error message and review of the case indicates that the codes are correct for the case, then the over-ride flag is used to skip the edit in the future. See Chapter IV, Recommended Data Edits and Software Coordination of Standards. Over-ride Flag as Used in the EDITS Software Package If Sequence Number-Central indicates the person has had more than one primary, then any case with one of the following Primary Site/Histologic Type ICD-O-3 combinations requires review: C760-C768 (ill-defined sites) or C809 (unknown primary) and Histologic Type ICD-O-3 < 9590. C77_ and Histologic Type ICD-O-3 not in range 9590-9729. C420-C424 and Histologic Type ICD-O-3 not in range 9590-9989. Any site code and Histologic Type ICD-O-3 in range 9740-9758. Instructions for Coding Code 1 can be used if a second or subsequent primary reporting with an ill-defined primary site has been reviewed and is indeed an independent primary... NAACCR Data Standards and Data Dictionary Version 11

Arbitrary; CA; Ill defined site O/R; Misc; Miscellaneous; Oncology; Ordinal; Other; Point in time; QL; Qual; Qualitative; Random; Screen; Spec; To be specified in another part of the message; TUMOR REGISTRY(NAACCR); Unspecified

Where you may see this code

You may see this code in lab systems, lab reports, EHR exports, interoperability feeds, or other structured clinical data exchanges.

Common synonyms

Ill defined site override flag Cancer caseIll defined site O/R Cancer caseIll defined site override flagTUMRRGTArbPtCancer case.XXX

Frequently asked questions

Code details

Code21998-0

SystemLOINC

Display nameIll defined site override flag Cancer case

DescriptionIll defined site override flag

Short nameIll defined site O/R Cancer case

ComponentIll defined site override flag

PropertyArb

TimingPt

System (specimen)Cancer case.XXX

ScaleOrd

ClassTUMRRGT

StatusACTIVE

Flags

BillableNo

Valid clinical useNo

Source

SourceLOINC

Version2.82

Releasemain

First released1.0m

Last changed2.27

Part names

Ill defined site override flagArbPtCancer case.XXXOrdArbitraryPoint in time (spot)Cancer case XXX

About this content

This page is prepared by HealthAssure's clinical team using official coding standards from LOINC. AI tools assist with drafting explanations, which are then reviewed and verified by healthcare professionals for accuracy. This content is for informational purposes and does not replace professional medical advice. Meet our team.