What prefix in the AJCC TNM staging system indicates stage determination at autopsy?

In the AJCC TNM staging system, the prefix that indicates stage determination at autopsy is "a." This designation is used when the cancer's stage is determined post-mortem, reflecting the findings from an autopsy rather than from clinical assessment or surgical findings during a patient's life.

The use of "a" allows for a clear distinction between stages assigned based on clinical evaluations and those determined retrospectively after death. This is important for maintaining the accuracy and consistency of staging data, as it signals to clinicians and researchers that these cases were assessed under different circumstances than those typically encountered in living patients.

Other prefixes in the AJCC TNM system have specific meanings; for instance, "c" denotes clinical staging based on pre-treatment examinations, "p" refers to pathological staging after surgical resection, and "r" is used for residual disease post-treatment. Each prefix serves a unique role in capturing the timing and context of stage determination, which aids in accurate reporting and analysis of cancer data.