R1 resection is a surgical pathology term that describes a cancer operation where tumor cells are found at the cut edge (the “margin”) under a microscope. In plain terms, it means the tumor was removed, but microscopic cancer may still be left behind at the surgical boundary. It is commonly used in surgical oncology reports for solid tumors, alongside R0 (clear margins) and R2 (visible residual tumor).

R0 resection means a tumor has been surgically removed with **no cancer seen at the cut edges (margins) under a microscope**. It is a standard term used in **surgical oncology** and **pathology reports** for many solid tumors. R0 resection describes the **quality of tumor removal**, not a specific surgical technique.

Margins are the edges or borders of tissue around a tumor. They are most commonly discussed after cancer surgery and in the pathology report. Margins help describe whether tumor cells extend to the cut surface of the removed tissue. They are also used in radiation oncology and some ablation procedures to define treatment boundaries.

Tumor differentiation describes how closely cancer cells look and behave like the normal cells they came from. It is usually reported by a pathologist after a biopsy or surgery. It helps summarize how “mature” or “specialized” the tumor cells appear under the microscope. It is commonly used in pathology reports, tumor grading, and treatment planning discussions.

Mitotic index is a measure of how many cells in a tissue sample are actively dividing. It is commonly assessed by a pathologist when a biopsy or surgery sample is examined under a microscope. In cancer care, it helps describe how quickly a tumor may be growing. It is often reported as part of a tumor’s grade or risk assessment.

Ki-67 index is a lab measurement that estimates how many tumor cells are actively dividing. It is reported as a percentage based on staining of a biopsy or surgical tissue sample. Clinicians use it most often in cancer pathology reports to describe tumor “proliferation” (growth activity). It is commonly discussed in solid tumors and some blood cancers, alongside tumor grade and stage.

WHO grading is a standardized way to describe how a tumor looks under the microscope and how aggressive it may behave. It is published within World Health Organization (WHO) tumor classification systems used by pathology and oncology teams. WHO grading is commonly reported after a biopsy or surgery when a pathologist examines tumor tissue. It helps clinicians communicate risk and plan care, alongside staging and other test results.

Fuhrman grade is a way pathologists describe how aggressive certain kidney cancers appear under a microscope. It is based on how the tumor cell nuclei look, including size, shape, and how prominent nucleoli are. It is most commonly discussed in renal cell carcinoma (RCC), especially clear cell RCC. It appears on a pathology report after a biopsy or surgery removes tumor tissue.

Bloom-Richardson grade is a pathology grading system that describes how aggressive an invasive breast cancer appears under the microscope. It summarizes several microscopic features into a single grade that helps communicate tumor behavior. It is most commonly reported for invasive breast carcinoma in biopsy or surgery pathology reports. It is sometimes referred to as the Nottingham (Elston–Ellis) histologic grade in many clinical settings.

Elston-Ellis grade is a pathology grading system used most commonly for invasive breast cancer. It describes how abnormal the cancer cells and tissue architecture look under a microscope. The grade helps summarize tumor “differentiation,” meaning how much the tumor resembles normal breast tissue. Clinicians use it alongside stage and biomarker results to understand prognosis and plan care.