The term “brain tumor” often evokes concern, though it encompasses a wide variety of abnormal growths within the skull. While public understanding often focuses on the most aggressive forms, many growths in the brain and central nervous system are non-cancerous. These non-malignant masses are significantly more common than their malignant counterparts. Understanding the frequency of these growths requires looking past the general perception of brain cancer to examine the specific statistics of non-cancerous tumors. This analysis focuses on the data surrounding these growths to provide a clearer picture of their occurrence.
Defining “Benign” in the Context of Brain Tumors
A tumor is classified as “benign” based on its biological behavior and growth characteristics within the central nervous system. This classification primarily means the tumor is non-cancerous, as the cells that compose the mass do not possess the aggressive features of malignancy. Benign tumors are typically slow-growing, and their cells look relatively normal when examined under a microscope. They generally remain confined to their original site and do not invade the surrounding brain tissue.
These masses often have distinct, clear boundaries, which makes them easier for surgeons to remove completely. A benign brain tumor does not metastasize, meaning it will not spread to other parts of the body, such as the lungs or liver. While they do not spread elsewhere, their location within the confined space of the skull can still cause serious health issues by pressing on delicate brain structures. The non-malignant nature of these tumors is reflected in a high five-year survival rate, which stands at approximately 91.7% for primary non-malignant central nervous system tumors in the United States.
Overall Incidence and Prevalence Rates
Non-malignant brain and central nervous system tumors occur at a much higher rate than many people realize. Based on data spanning from 2018 to 2022, the average annual age-adjusted incidence rate for non-malignant primary tumors in the United States was 19.19 cases per 100,000 people. This rate suggests that non-malignant tumors are the most common type of primary central nervous system tumor diagnosed each year. For instance, in 2025 alone, an estimated 80,610 new cases of non-malignant brain and central nervous system tumors are expected to be diagnosed in the United States.
These incidence rates are monitored by organizations like the Central Brain Tumor Registry of the United States (CBTRUS). Accurate tracking of these statistics presents unique challenges because, historically, not all non-malignant tumors were required to be reported to state and national registries. The prevalence of these tumors—the total number of individuals living with a diagnosis—is also high, with data showing that the majority of all individuals living with a brain tumor diagnosis have a non-malignant type. Since the collection of comprehensive data on both malignant and non-malignant tumors is relatively recent, older statistics likely underreport the true frequency of benign masses.
The overall incidence rate is notably higher in females compared to males, at 29.67 versus 22.23 per 100,000 population, largely driven by the high occurrence of a specific benign tumor type. This demographic difference highlights the variability in tumor occurrence across the population. Furthermore, the overall incidence rate of all primary central nervous system tumors is highest in adults over the age of 40.
The Most Frequently Diagnosed Benign Tumor Types
The high incidence rate of non-malignant tumors is largely accounted for by a few specific tumor types that arise from the membranes and glands near the brain. Meningiomas are by far the most common non-malignant tumor, representing approximately 42.6% of all primary brain and central nervous system tumors and 57.4% of all non-malignant tumors. These growths originate from the meninges, the layers of tissue that cover the brain and spinal cord. Meningiomas are responsible for the higher incidence rates seen in women, as they occur more frequently in the female population.
The next most frequently diagnosed non-malignant tumors are Pituitary Adenomas, which arise within the pituitary gland at the base of the brain. The reported annual incidence rate for these tumors is approximately 4.28 per 100,000 population. Pituitary adenomas are typically slow-growing and often cause symptoms by disrupting the normal hormone production of the gland, or by pressing on the optic nerves. These tumors are highly prevalent in adults, often affecting individuals in their 30s and 40s.
Vestibular Schwannomas, often called acoustic neuromas, represent another significant portion of benign central nervous system tumors. These tumors develop on the vestibular nerve, which connects the inner ear to the brain and is responsible for hearing and balance. Schwannomas are generally slow-growing and are most frequently diagnosed in adults between the ages of 30 and 60. While less common than meningiomas and pituitary adenomas, they are a primary example of how a non-malignant tumor can still cause serious neurological symptoms, such as hearing loss or dizziness, due to its precise location.
Comparing Benign and Malignant Tumor Incidence
Non-malignant tumors are significantly more common than malignant tumors among newly diagnosed primary central nervous system tumors. Data shows that non-malignant tumors make up approximately 73.7% of all primary central nervous system tumors, while malignant ones account for 26.3%. This means that for every one diagnosis of a malignant brain tumor, there are more than two diagnoses of a non-malignant one.
The average annual age-adjusted incidence rate for non-malignant tumors is 19.19 per 100,000 population, which is higher than the 6.86 per 100,000 population rate for malignant tumors. This statistical difference underscores that the majority of primary masses found in the brain are not cancerous. Understanding the greater overall frequency of non-malignant tumors is essential for grasping the full scope of brain tumor diagnoses.