Nuclear grade is a score that describes how abnormal the nuclei of tumor cells look under the microscope. The nucleus is the part of the cell that holds its genetic material. The more the nuclei differ from those of normal cells, the higher the nuclear grade.
Nuclear grade is most often reported for breast cancer and kidney cancer. It is usually given as a number, such as 1, 2, or 3, or as a word, such as low, intermediate, or high. This article explains what nuclear grade measures, how it relates to the overall grade of a tumor, and what it means in your pathology report.
To assign a nuclear grade, a pathologist compares the nuclei of the tumor cells with the nuclei of normal cells from the same organ. The features the pathologist looks at include:
Each cancer type that uses nuclear grade has its own rules for scoring these features.
The grade of a tumor describes how different the tumor looks from normal tissue. Nuclear grade looks only at the nuclei. The overall grade may also consider how the cells are arranged and how quickly they are dividing.
In some cancers, nuclear grade is the whole grade. In others, it is one part of a larger grading system. For example, the Nottingham histologic grade for invasive breast cancer adds a nuclear score to two other scores to produce the final grade.
Nuclear grade is reported for several tumor types. The most common examples are:
Not every tumor is given a nuclear grade. For example, chromophobe renal cell carcinoma is not graded this way, because its nuclei often look abnormal even though the tumor usually behaves favorably.
In general, a higher nuclear grade means the tumor cells look more abnormal. Tumors with a higher nuclear grade tend to grow faster. They are also more likely to come back after treatment or spread to other parts of the body. Tumors with a lower nuclear grade tend to grow more slowly.
Nuclear grade is only one of several factors that describe a tumor. Your doctors will consider it along with the tumor size, margins, stage, and other test results. For some tumors, such as DCIS, the nuclear grade is one of the factors considered when deciding on treatment after surgery.
Yes. A biopsy removes only a small part of the tumor, and different areas of a tumor can have different nuclear grades. When the whole tumor is removed, the pathologist may find an area with a higher grade than the biopsy showed. In most systems, the pathologist reports the highest grade seen, even if it is present in only part of the tumor.