How are ICD-O-3 histology codes used in registries?

• A. They record patient dietary habits.
• B. They classify tumor morphology (4-digit code) and support site-specific coding, prognosis, and survival analyses.
• C. They set insurance reimbursement rates.
• D. They identify hospital department responsible for registry data.

Answer: (B)

ICD-O-3 histology codes are used to classify tumor morphology with a four-digit code and to connect that morphology to the tumor’s site. This standardization lets registries categorize cancers consistently across different institutions and time periods, enabling site-specific coding where the histology is interpreted within the appropriate anatomical context. Because different histologies within the same site can have distinct prognoses and survival patterns, these codes support meaningful prognosis and survival analyses and allow researchers to stratify data accurately. They also facilitate data comparability and quality across registries, which is crucial for epidemiologic studies and trend analyses over years and regions. The other options don’t reflect what ICD-O-3 histology codes do: they don’t capture dietary habits, set reimbursement rates, or identify the hospital department responsible for registry data.