Globally, in 2018, 1.6% of all new cancers were brain tumors, and an estimated 2.5% of all cancer-related deaths were due to brain tumor (1). The prevalence of brain tumors varies according to sex, age at diagnosis, geographical location, race, histologic type, and genetic and environmental risk factors, and may exhibit temporal incidence trends (2). The annual number of new cases based on pathology was 654 577 (68%) benign tumors and 302 715 (32%) malignant brain tumors in 2019. Africa reported 82, 481 (8%) new annual cases (3). Kenya had 675 (1.4%) new cases of brain tumors, and the 5-year prevalence of brain tumors of all ages was 1 352 (2.65%) (4). Low reporting may explain the low incidence, prevalence, and mortality rates in some Asian and sub-Saharan African countries, which often lack registries, or the existing registries do not include brain tumors (2). Brain tumors exhibit a bimodal age distribution, with peaks in incidence, both in childhood and adulthood between 45–70 years (2). Notably, in children under the age of 15 years, brain tumors are the most commonly diagnosed solid tumors (5), whereas brain metastases (BMs) are the most isolated brain tumors in adults (6). Pilocytic astrocytomas and embryonal tumors are common in children, whereas meningiomas, malignant gliomas, and pituitary adenomas are mainly diagnosed in adults (7, 8).
Meningiomas and glioblastomas are the most common benign and malignant brain tumors, diagnosed in women and men, respectively (9, 10). According to the Central Brain Tumors Registry of the United States (CBTRUS), of all brain tumors diagnosed between 2012–2016 in the United States, 69.8% were benign, half of which were meningiomas, while an estimated 30.2% were malignant, with glioblastomas being the most common (10). Malignant brain tumors are largely due to brain metastases and are fourfold of primary tumors. The increased prevalence of brain metastases is attributed to improved cancer care, and thus cancer patients live longer with an estimated 20–40% likelihood of developing brain tumors (11). Primary cancers of the lung, breast, melanoma, and kidney are most likely to metastasize; however, any primary cancer can generally metastasize (12, 13). Primary malignant brain tumors also significantly contribute to malignant brain tumors (14).
Imaging studies, primarily magnetic resonance imaging (MRI) and computed tomography (CT), are used to locate brain tumors (15). The definitive diagnosis is established by histological examination and further characterization by immunohistochemistry (IHC) and molecular studies, where available (16). Historically, the diagnosis and classification of brain tumors have been based solely on the histological presentation of the tumor using light microscopy. The integration of molecular techniques in diagnosing brain tumors has enabled the molecular classification of brain tumors and potential improvement in diagnostic accuracy, patient management, and objective monitoring of treatment (16). The current WHO classification of the central nervous system (CNS) standard integrates the molecular characterization of brain tumors with conventional techniques, such as histology and immunohistochemistry. However, in institutions where molecular resources are unavailable, histological diagnosis is sufficient to diagnose brain tumors (16). There are inadequate and noncomprehensive data on the prevalence of brain tumors, as evidenced by the limited existence of cancer registries, especially for brain tumors in low- and middle-income countries (2, 17). Therefore, this study aimed to determine the prevalence and pattern of brain tumors in a national referral hospital in Nairobi, Kenya.