#1: Tumor size
Source 1: 2018 SEER Manual
Notes: Tumor Size--Clinical
Tumor Size--Clinical--Breast: Does information from any type of biopsy take precedence over an imaging report? See Discussion.
For example, a patient has a 2.6 cm breast tumor on MRI; a core biopsy measuring 0.7 cm is positive for infiltrating duct carcinoma. Rule #1 states "Use the largest measurement of the primary tumor from physical exam, imaging, or other diagnostic procedures before any form of treatment." However, Rule #9 seems to imply that size from an "incisional biopsy" takes precedence over imaging, even though it is known to be less than the entire tumor in size.
We do not recommend using the size from a core biopsy for clinical tumor size. A core biopsy does not necessarily obtain enough tissue to know the actual tumor size. Since there is imaging for this patient, it is preferable to record clinical tumor size from the imaging report in this case.
The instructions will be clarified in the next revision of the SEER manual.