A low grade tumor refers to a mass of abnormal cells that are slowly growing and look almost normal under a microscope. Low grade tumors tend to be less aggressive than high grade tumors, and many are considered benign (non-cancerous). However, some low grade tumors can be malignant (cancerous). The grade of a tumor is one factor doctors consider when determining treatment plans and prognosis.
Quick answers
Here are quick answers to key questions about low grade tumors:
- Yes, some low grade tumors are benign while others are malignant.
- Low grade means the cells look more normal and are growing more slowly compared to higher grade tumors.
- Doctors determine whether a low grade tumor is benign or malignant based on its microscopic appearance, location, and other factors.
- Examples of benign low grade tumors include uterine fibroids, some types of brain tumors, and papillomas.
- Examples of malignant low grade tumors include low grade astrocytomas in the brain and low grade sarcomas.
- Benign low grade tumors can often be safely monitored over time or removed if causing problems. Malignant low grade tumors usually require treatment.
Determining if a tumor is benign vs malignant
Doctors consider several factors when evaluating whether a low grade tumor is benign or malignant:
- Microscopic appearance – Benign tumors tend to have cells that look more normal and are growing more slowly. Malignant tumors have more abnormal looking cells.
- Location – A tumor that develops in a site where normal tissue is not present is more likely to be malignant. Tumors within normal structural tissue are more often benign.
- Rate of growth – Faster growing tumors are more concerning for malignancy. Benign tumors tend to grow slowly over months or years.
- Blood vessel growth – Benign tumors generally have few blood vessels supplying nutrients. Malignant tumors generate new blood vessels in a process called angiogenesis.
- Invasion – Benign tumors tend to stay in one location and do not invade other tissues. Malignant tumors can invade and damage nearby tissue.
- Metastasis – Benign tumors do not spread to other parts of the body. Malignant tumors can metastasize and form secondary tumors elsewhere.
Using these factors, doctors examine the tumor cells under a microscope to determine if cancer is present. They may also order imaging tests and biopsies to gather more information.
Examples of benign low grade tumors
Many types of benign tumors are low grade. Common examples include:
- Uterine fibroids – Noncancerous tumors that develop in the smooth muscular tissue of the uterus. Often slow growing and cause no symptoms.
- Lipomas – Benign fat cell tumors that form lump under the skin, usually on the trunk, neck, or arms. Generally painless.
- Hepatic adenomas – Benign liver tumors arising from liver cells called hepatocytes. More common in women taking oral contraceptives.
- Osteochondromas– Benign bone tumors capped with cartilage that often develop next to joints or growth plates in children and adolescents.
- Schwannomas – Slow growing tumors derived from Schwann cells which produce the insulating myelin sheath covering peripheral nerves.
- Papillomas – Benign tumors derived from epithelial cells that line organs. Include common skin warts and polyps in the colon, bladder, larynx, etc.
- Pituitary adenomas – Benign tumors of the pituitary gland that can affect hormone production and put pressure on surrounding structures.
- Meningiomas – Slow growing tumors arising from the meninges membrane layers covering the brain and spinal cord.
These benign tumors often do not require treatment beyond regular monitoring. However, some may be removed if they are causing symptoms, growing rapidly, or at risk of turning malignant.
Examples of malignant low grade tumors
While less common than high grade cancers, there are malignant tumors that are categorized as low grade, including:
- Low grade astrocytomas – Cancers arising from star-shaped glial cells called astrocytes in the brain or spinal cord. Can be a mix of slow growing and aggressive areas.
- Low grade sarcomas – Cancers of connective tissues like muscle, fat, cartilage, and bone. Examples are low grade myxofibrosarcoma and liposarcoma.
- Bronchial carcinoids – Slow growing neuroendocrine tumors arising from hormone-producing Kulchitsky cells lining the lungs.
- Early stage bladder cancer – Some non-muscle invasive bladder cancers are low grade when first detected but require treatment to prevent recurrence.
- Low grade neuroendocrine tumors (NETs) – Cancers of neuroendocrine cells that control digestion, respiration, metabolism, reproduction, and other processes.
- Low grade lymphomas – Cancers of lymphocytes, a type of white blood cell. Includes some forms of non-Hodgkin lymphoma characterized by enlarged lymph nodes.
Despite being low grade, these malignant tumors can invade surrounding tissues and spread to other areas of the body. Treatment typically involves some combination of surgery, radiation therapy, chemotherapy, and other systemic therapies.
Rates of benign vs. malignant for common low grade tumors
The likelihood that a particular type of low grade tumor is benign or malignant can vary considerably. Here are estimated rates for some common tumors:
| Type of Tumor | % Benign | % Malignant |
|---|---|---|
| Uterine fibroids | 100% | 0% |
| Lipomas | 100% | 0% |
| Osteochondromas | 90-95% | 5-10% |
| Schwannomas | 95% | 5% |
| Colonic polyps | 80-90% | 10-20% |
| Pituitary adenomas | 90% | 10% |
| Low grade astrocytomas | 0% | 100% |
| Low grade sarcomas | 0% | 100% |
| Bronchial carcinoids | 10% | 90% |
| Low grade lymphomas | 0% | 100% |
As shown, the likelihood of a low grade tumor being benign or malignant can range significantly depending on the type. Uterine fibroids, lipomas, and osteochondromas are almost always benign. Meanwhile, certain sarcomas and lymphomas are always cancerous even when low grade.
Diagnosing low grade tumors
Doctors use a number of tests to evaluate low grade tumors:
- Medical history and physical exam – Looking for risk factors and suspicious signs upon examination of the body.
- Imaging – CT scans, MRIs, ultrasounds, and PET scans create detailed images that show tumor location, size, and properties.
- Biopsy – Removing a small sample of the tumor for microscopic examination to determine if cancer cells are present.
- Lab tests – Testing blood, urine, or tumor tissue samples for abnormal hormone levels, genetic mutations, and other markers.
- Endoscopy – Using a thin, lighted tube with a camera to view tumors inside the body cavities and hollow organs.
These tests allow doctors to confirm that a tumor is present, determine whether it is likely benign or malignant, and establish an accurate grade and stage if cancerous. This guides appropriate treatment.
Treatment options for low grade tumors
Treatment plans vary depending on whether a low grade tumor is benign or malignant:
- Benign tumors – May be monitored without treatment, surgically removed, or treated with non-surgical techniques like embolization or ablation to block blood supply or destroy tumor cells.
- Malignant tumors – Often require some combination of surgery, radiation therapy, chemotherapy, immunotherapy, hormone therapy, or other treatments based on the type and stage of cancer.
Determining the optimal treatment course involves assessing the tumor’s location, size, extent of spread, and other characteristics, as well as considering the patient’s overall health.
Monitoring and prognosis of low grade tumors
The monitoring and outlook for low grade tumors depends on multiple factors:
- Benign tumors typically have an excellent prognosis when monitored or removed. However, some benign tumors can eventually become malignant.
- Malignant low grade tumors generally have better prognoses than high grade cancers. However, they require appropriate treatment to prevent recurrence and spread.
- Larger tumors tend to have a worse prognosis than smaller tumors for both benign and malignant cases.
- Low grade tumors that arise in certain locations, like the brain or lungs, can be more risky due to their positions.
- Rarely, a cancer that appears low-grade initially may increase in aggressiveness and become higher grade over time.
Regular physical exams, imaging tests, lab work, and biopsies are crucial for monitoring low grade tumors, spotting concerning changes early, and guiding any adjustments in treatment.
Conclusion
While many low grade tumors are benign, others can be malignant cancers even though they are slower growing. Determining whether a low grade tumor is benign vs. malignant involves microscopic analysis along with considering the tumor’s location and other characteristics. Benign low grade tumors often don’t require treatment beyond monitoring, while malignant ones usually necessitate surgery, radiation, chemotherapy, or other interventions. Careful tracking and follow up is important for ensuring the best outcomes.