Low grade cancer refers to a classification based on how the cancer cells appear under a microscope. This grading provides an indication of how slowly or quickly a tumor is likely to grow and spread throughout the body. Low grade tumors are composed of cells that still closely resemble normal, healthy cells from the tissue where the cancer originated. This similarity suggests that the cellular processes of growth and division are less aggressive compared to high grade cancers.
Understanding Cancer Grading vs. Staging
Grading refers to the microscopic appearance of cancer cells, specifically how differentiated they are from normal cells. Staging, conversely, is a measure of the disease’s physical extent within the body. Staging involves assessing the tumor’s size, whether it has spread to nearby lymph nodes, and if it has metastasized to distant organs.
This distinction is important because a low grade tumor, which is less aggressive, can still be found at a high stage if it has physically spread throughout the body. Similarly, a high grade cancer, which is biologically aggressive, might be localized and considered a low stage. Physicians use both the grade and the stage together to create a complete picture of the cancer’s severity and determine the appropriate course of action.
Cellular Characteristics of Low Grade Tumors
Low grade classification is based on specific features a pathologist observes when examining cells and tissue architecture. Low grade tumors are described as “well-differentiated,” meaning the cells maintain a structure and organization very similar to the original healthy tissue.
Another characteristic of low grade tumors is a low mitotic rate, which is the frequency of cell division observed within the sample. In low grade tumors, the number of cells actively undergoing mitosis is small, suggesting a slow rate of growth. The nuclei of these cells also appear less irregular, showing minimal variation in size and shape, a feature known as low nuclear pleomorphism.
Determining the Cancer Grade
Determining a cancer’s grade begins with obtaining a tissue sample, typically through a biopsy or surgical removal. This tissue is then processed and stained before being examined under a microscope by a specialist called a pathologist. The pathologist evaluates the cellular and architectural features of the tumor to assign a grade.
For many cancers, a standard numerical scale is used, often ranging from Grade 1 (low grade) to Grade 3 or 4 (high grade). However, some cancers have specialized grading systems that incorporate multiple factors into a single score. For instance, prostate cancer is graded using the Gleason score, where two dominant patterns of cell growth are scored and added together to produce a final value, with a score of 6 being the lowest grade.
Implications for Treatment and Prognosis
A low grade classification suggests a more favorable long-term outlook compared to high grade cancer, due to the tumor’s slower growth rate and reduced likelihood of metastasis. The less aggressive nature of these tumors often allows for less immediate and less intensive treatment strategies. For certain low grade cancers, particularly low-risk prostate cancer, a management approach called Active Surveillance may be recommended.
Active Surveillance involves regular monitoring of the tumor with tests like PSA screenings, imaging, and repeat biopsies, rather than immediate intervention. The goal is to avoid the potential side effects of aggressive treatments, such as surgery or radiation, for a tumor that may never cause harm. Treatment is only initiated if monitoring indicates signs of progression to a higher grade or more advanced stage. When low grade tumors require intervention, treatment is often localized, involving targeted surgery or radiation to remove or destroy the tumor.