Which classification system was implemented in 2001 to classify tumors based on their characteristics?

The classification system implemented in 2001 to classify tumors based on their characteristics is indeed ICD-O-3. The ICD-O-3, or the International Classification of Diseases for Oncology, Third Edition, is specifically designed for the classification of neoplasms (tumors) and incorporates both the histological type and the behavior of the tumor. This system is essential for cancer registries and epidemiology, offering a standardized method to classify cancer cases based on their anatomical sites and histological types, which facilitates research and data collection on cancer incidence.

Other classification systems mentioned serve different purposes. ICD-10-PCS is a procedural coding system used for inpatient hospital setting procedures, while CPT is used for reporting medical services and procedures performed by healthcare providers. ICD-10-CM, on the other hand, focuses on the diagnosis coding for a wide range of diseases and is not specifically tailored for oncology. Therefore, ICD-O-3 stands out as the appropriate answer for classifying tumors based on their characteristics.