kb/data/en.wikipedia.org/wiki/Benign_tumor-1.md

title	chunk	source	category	tags	date_saved	instance
Benign tumor	2/3	https://en.wikipedia.org/wiki/Benign_tumor	reference	science, encyclopedia	2026-05-05T07:26:29.480012+00:00	kb-cron

==== 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. Structures such as the marrow cavity and cortical bone of the osteochondroma are contiguous to those of the originating bone. Sites of origin often involve metaphyses of long bones. While many osteochondromas occur spontaneously, there are cases in which several osteochondromas can occur in the same individual; these may be linked to a genetic condition known as hereditary multiple osteochondromas. Osteochondroma appears on X-ray as a projecting mass that often points away from joints. These tumors stop growing with the closure of the parental bone's growth plates. Failure to stop growth can be indicative of transformation to malignant chondrosarcoma. Treatment is not indicated unless symptomatic. In that case, surgical excision is often curative.

==== Enchondroma ==== Enchondromas are benign tumors of hyaline cartilage. Within a bone, enchondromas are often found in metaphyses. They can be found in many types of bone, including small bones, long bones, and the axial skeleton. X-ray of enchondromas shows well-defined borders and a stippled appearance. Presentation of multiple enchondromas is consistent with multiple enchondromatosis (Ollier Disease). Treatment of enchondromas involves surgical curettage and grafting.

=== Benign soft tissue tumors ===

==== Lipomas ==== Lipomas are benign, subcutaneous tumors of fat cells (adipocytes). They are usually painless, slow-growing, and mobile masses that can occur anywhere in the body where there are fat cells, but are typically found on the trunk and upper extremities. Although lipomas can develop at any age, they more commonly appear between the ages of 40 and 60. Lipomas affect about 1% of the population, with no documented sex bias, and about 1 in every 1000 people will have a lipoma within their lifetime. The cause of lipomas is not well defined. Genetic or inherited causes of lipomas play a role in around 2-3% of patients. In individuals with inherited familial syndromes such as Proteus syndrome or Familial multiple lipomatosis, it is common to see multiple lipomas across the body. These syndromes are also associated with specific symptoms and sub-populations. Mutations in chromosome 12 have been identified in around 65% of lipoma cases. Lipomas have also been shown to be increased in those with obesity, hyperlipidemia, and diabetes mellitus. Lipomas are usually diagnosed clinically, although imaging (ultrasound, computed tomography, or magnetic resonance imaging) may be utilized to assist with the diagnosis of lipomas in atypical locations. The main treatment for lipomas is surgical excision, after which the tumor is examined with histopathology to confirm the diagnosis. The prognosis for benign lipomas is excellent and recurrence after excision is rare, but may occur if the removal was incomplete.

== Mechanism ==

=== Benign vs malignant ===

A tumor is classified as either benign or malignant based on its invasive potential. Benign tumors are non-invasive: They cannot invade adjacent tissues or metastasize (spread via metastasis). In contrast, malignant tumors are invasive or metastatic. For this reason, benign tumors are not classed as cancer. A benign tumor will grow in a contained area, usually a fibrous connective tissue capsule. The growth rates of benign and malignant tumors usually differ, with benign tumors growing more slowly than malignant tumors. However, cases of fast-growing benign tumors have been documented. Although benign tumors generally pose a lower health risk than malignant tumors, both can be life-threatening. Benign and malignant tumors differ in some general characteristics, but sometimes a benign tumor will exhibit some characteristics of a malignant tumor, or vice versa. For example, benign tumors are mostly well-differentiated, and malignant tumors are often undifferentiated. However, undifferentiated benign tumors can occur, as can differentiated malignant tumors. Certain malignant tumors, such as basal-cell carcinomas, are mostly non-metastatic.

=== Multistage carcinogenesis ===

Tumors are formed by carcinogenesis, a process in which cellular alterations lead to the formation of cancer. Multistage carcinogenesis involves the sequential genetic or epigenetic changes to a cell's DNA, where each step produces a more advanced tumor. It consists of three stages: initiation, promotion and progression. Multiple mutations may occur per stage. Initiation is where the first genetic mutation occurs in a cell. Promotion is the clonal expansion (repeated division) of this transformed cell into a visible tumor that is usually benign. Following promotion, progression may take place where more genetic mutations are acquired in a sub-population of tumor cells. Progression changes the benign tumor into a malignant tumor. A prominent and well studied example of this phenomenon is the tubular adenoma, a common type of colon polyp which is an important precursor to colon cancer. The cells in tubular adenomas, like most tumors that frequently progress to cancer, show certain abnormalities of cell maturation and appearance collectively known as dysplasia. These cellular abnormalities are not seen in benign tumors that rarely or never turn cancerous, but are seen in other pre-cancerous tissue abnormalities which do not form discrete masses, such as pre-cancerous lesions of the uterine cervix.

== Diagnosis ==

=== Classification ===