Addressing concerns about cancer-causing substances, we propose a nuanced cancer classification scheme that considers both the mode of action and potency of substances. This approach provides more detailed guidance for the regulation and management of potentially carcinogenic substances, moving beyond oversimplified binary categorizations. The assessment of carcinogenic potential is evolving, with a shift from traditional long-term rodent bioassays to New Approach Methodologies (NAMs) that incorporate in vitro and in vivo studies. There is also a growing emphasis on limiting or prohibiting certain chemicals based on potential hazards. The Adverse Outcome Pathway (AOP) concept is applied to construct a comprehensive model for carcinogenesis, offering a unified framework to categorize various biological effects associated with cancer development and a systematic understanding of intricate pathways and mechanisms involved in carcinogenesis.

Initiation of the Process:

The process commences with mutations occurring in a stem cell during cell division, a common event in the cellular life cycle.

Frequency of Mutations:

The occurrence of this event is highly frequent, with an estimated production of 2 × 10^8 cells carrying mutations capable of leading to cancer throughout a human lifetime.

Survival and Tumorigenesis:

Despite the high mutation rate, a majority of these mutated cells either do not survive or fail to complete the tumorigenesis process.

Governance by Three Rates:

The overall process is regulated by three key rates:

Number of stem cell divisions per unit of time.

Rate of mutation per cell division, contributing to the emergence of cancer-associated mutations

Rate at which cancer-capable cells survive and progress, eventually evolving into a full-fledged cancer.