A benign tumor is a mass of cells (tumor) that does not invade neighboring tissue or metastasize (spread throughout the body). Compared to malignant (cancerous) tumors, benign tumors generally have a slower growth rate. Benign tumors have relatively well differentiated cells. They are often surrounded by an outer surface (fibrous sheath of connective tissue) or stay contained within the epithelium. Common examples of benign tumors include moles and uterine fibroids. Some forms of benign tumors may be harmful to health. Benign tumor growth causes a mass effect that can compress neighboring tissues. This can lead to nerve damage, blood flow reduction (ischemia), tissue death (necrosis), or organ damage. The health effects of benign tumor growth may be more prominent if the tumor is contained within an enclosed space such as the cranium, respiratory tract, sinus, or bones. For example, unlike most benign tumors elsewhere in the body, benign brain tumors can be life-threatening. Tumors may exhibit behaviors characteristic of their cell type of origin; as an example, endocrine tumors such as thyroid adenomas and adrenocortical adenomas may overproduce certain hormones. Many types of benign tumors have the potential to become cancerous (malignant) through a process known as tumor progression. For this reason and other possible harms, some benign tumors are removed by surgery. When removed, benign tumors usually do not return. Exceptions to this rule may indicate malignant transformation. Signs and symptoms
Benign tumors are very diverse; they may be asymptomatic or may cause specific symptoms, depending on their anatomic location and tissue type.
One role of pVHL is to cause the cellular degradation of another protein, HIF1α. Dysfunctional pVHL leads to accumulation of HIF1α. This activates several genes responsible for the production of substances involved in cell growth and blood vessel production: VEGF, PDGFβ, TGFα and erythropoietin. Bone tumors
Benign tumors of bone can be similar macroscopically and require a combination of a clinical history with cytogenetic, molecular, and radiologic tests for diagnosis. Three common forms of benign bone tumors with are giant cell tumor of bone, osteochondroma, and enchondroma; other forms of benign bone tumors exist but may be less prevalent. Giant cell tumors
Giant cell tumors of bone frequently occur in long bone epiphyses of the appendicular skeleton or the sacrum of the axial skeleton. Local growth can cause destruction of neighboring cortical bone and soft tissue, leading to pain and limiting range of motion. The characteristic radiologic finding of giant cell tumors of bone is a lytic lesion that does not have marginal sclerosis of bone. On histology, giant cells of fused osteoclasts are seen as a response to neoplastic mononucleated cells. Notably, giant cells are not unique among benign bone tumors to giant cell tumors of bone. Molecular characteristics of the neoplastic cells causing giant cell tumors of bone indicate an origin of pluripotent mesenchymal stem cells that adopt preosteoblastic markers. Cytogenetic causes of giant cell tumors of bone involve telomeres. Treatment involves surgical curettage with adjuvant bisphosphonates. Osteochondroma
Osteochondromas form cartilage-capped projections of bone.