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  • Osteochondromas or osteocartilaginous exostoses are the most common benign

  • tumors of the bones. The tumors take the form of cartilage-capped bony

  • projections or outgrowth on the surface of bones. It is characterized as a type

  • of overgrowth that can occur in any bone where cartilage forms bone. Tumors most

  • commonly affect long bones in the leg, pelvis, or scapula. Development of

  • osteochondromas take place during skeletal growth between the ages of 13

  • and 15 and ceases when the growth plate fuses at puberty. They arise within the

  • first three decades of life affecting children and adolescents.

  • Osteochondromas occur in 3% of the general population and represent 35% of

  • all benign tumors and 8% of all bone tumors. Majority of these tumors are

  • solitary non-hereditary lesions and approximately 15% of osteochondromas

  • occur as hereditary multiple osteochondromas. They can occur as a

  • solitary lesion or multiple lesions within the context of the same bone.

  • Osteochondromas do not result from injury and the exact cause remains

  • unknown. Recent research has indicated that multiple osteochondromas is an

  • autosomal dominant inherited disease. Germ line Mutations in EXT1 and EXT2

  • genes located on chromosomes 8 and 11 have been associated with the cause of

  • the disease. The treatment choice for osteochondroma is surgical removal of

  • solitary lesion or partial excision of the outgrowth, when symptoms cause

  • motion limitations or nerve and blood vessel impingements.

  • Mechanism Osteochondromas are long and slender,

  • pedunculated on a stalk often taking the shape of a cauliflower. The cartilage

  • cap is covered by fibrous perichondrium and continues with the periosteum of the

  • underlying bone. The cartilage cap is less than 2 cm thick and the thickness

  • decreases with age. A cap more than 2 cm thick, indicates malignant

  • transformation of a tumor. The cartilage cap merges with the epiphyseal area of

  • the long bones called spongiosa. In the spongiosa, the chondrocytes are arranged

  • in accordance with the epiphyseal growth plate. The spongiosa of the stalk

  • continues with the underlying cancellous bone. Fractures within the stalk causes

  • fibroblastic proliferation and formation of a new bone. Development of bursa

  • takes place over the osteochondroma, which is attached to the perichondrium

  • of the cap. Inflammation of the bone is indicated by the bursal wall lined by

  • the synovium. As a result, patients may have swelling for years related to the

  • location and site of the lesion indicative of mechanical obstruction,

  • nerve impingement, pseudoaneurysm of the overlying vessel, fracture at the stalk

  • of the lesion, or formation of bursa over the osteochondroma. Heparan

  • sulphate are glycosaminoglycans which are involved in the formation of

  • proteoglycans. The biosynthesis of HS takes place in the Golgi apparatus and

  • Endoplasmic Reticulum, where glycosaminoglycans chains are maintained

  • by type II glycosyltransferases encoded by EXOSTOSIN genes EXT1 and EXT2.

  • Decreased levels of HS leads to mutations in EXT1 or EXT2 causing

  • skeletal abnormality. The underlying mechanism for solitary and multiple

  • osteochondromas have been associated with genetic alterations in EXT1 or EXT2

  • genes located on chromosomes 8 and 11. Approximately 65% of osteochondromas

  • arise in the EXT1 gene loci on chromosome 8 and 35% arise in EXT2 gene

  • loci on chromosome 11. About 70–75% of multiple osteochondromas are caused by

  • point mutations, often involving deletion of single or multiple axons as

  • found in 10% of all hereditary cases. In about 10–15% of all cases no genomic

  • alterations are detected. The mechanism behind the formation of multiple

  • osteochondroma is large genomic deletions of EXT1 and EXT2 genes. The

  • identified mechanism behind solitary osteochondromas is the homozygous

  • deletions of the EXT1 gene. However, the exact cause of osteochondroma is

  • unknown. Additionally, the molecular basis of genetics and clinical

  • variability of multiple osteochondroma as well as the underlying causes for the

  • malignant transformation and the onset of osteochondroma in EXT negative

  • patients is also currently unknown. Symptoms

  • Limited normal functions and movements are caused by osteochondromas growing

  • slowly and inwardly. The majority of osteochondromas are symptomless and are

  • found incidentally. Each individual with osteochondroma may experience symptoms

  • differently and most of the time individuals will experience no symptoms

  • at all. Some of the most common symptoms are a hard immobile painless palpable

  • mass, adjacent muscle soreness, and pressure or irritation with heavy

  • exercising. Major symptoms arise when complications such as fractures, bone

  • deformity or mechanical joint problems occur. If the occurrence of an

  • osteochondroma is near a nerve or a blood vessel, the affected limb can

  • experience numbness, weakness, loss of pulse or color change. Periodic changes

  • in the blood flow can also take place. Approximately 20% of patients

  • experiencing nerve compression commonly acknowledge vascular compression,

  • arterial thrombosis, aneurysm, and pseudoaneurysm. Formation of

  • pseudoaneurysm and venous thrombosis lead to claudication, pain, acute

  • ischemia, and symptoms of phlebitis. If the tumor is found under a tendon, it

  • can cause pain during movement causing restriction of joint motion. Pain can

  • also occur due to bursal inflammation, swelling or fracture at the base of the

  • tumor stalk. Some of the clinical signs and symptoms of malignant osteochondroma

  • are pain, swelling, and mass enlargement.

  • Diagnosis Osteochondromas are often asymptomatic

  • and may not cause any kind of discomfort. They are often found

  • accidentally when an X-ray is done for an unrelated reason.

  • X-rays are the first tests performed that characterize a lesion. They show a

  • clear picture of dense structures of bones, and will also indicate bone

  • growth pertaining to osteochondroma. Computed Tomography scan can identify

  • the bony lesion in great details and show the presence of calcification.

  • These tests also provide great details, especially in soft tissues with the aide

  • of cross-sectional images. Magnetic Resonance Imaging is the most

  • accurate method for detecting bone masses in symptomatic cases to depict

  • precise morphology of a tumor. It is used to verify if the palpable mass is

  • continuous with the cortex of the affected bone and to differentiate an

  • osteochondroma from other lesions on the surface of the bone. MRI can also be

  • used to look for cartilage on the surface of tumor and can depict any

  • vascular complications caused by the tumor. An MRI can identify tumors of the

  • spinal column and is often used to diagnose low grade osteosarcoma.

  • Ultrasound is done if aneurysms or pseudoaneurysms and venous or arterial

  • thrombosis is suspected. Ultrasound is an accurate method for examining the

  • cartilaginous cap of the osteochondroma. It is also a way of pinpointing

  • bursitis. However, it cannot be used to predict if the growth of tumor is inward

  • in regards to the cap. Angiography is used to detect vascular

  • lesions caused by osteochondroma due to ossified cartilaginous cap. It is also

  • used to characterize malignant transformation lesions through

  • neovascularity. Clinical testing such as sequence

  • analysis can be done of the entire coding regions of both EXT1 and EXT2 to

  • detect mutations. A biopsy of the tissue sample of the

  • tumor can also be taken to check for cancer.

  • Tests for osteochondroma can also identify diseases such as secondary

  • peripheral chondrosarcoma and Multiple osteochondromatosis. In large, secondary

  • chondrosarcoma arises at the site of osteochondroma due to increased

  • thickness of the cartilage cap indicating potential malignant

  • transformation. The symptoms of multiple osteochondromatosis are similar to

  • solitary osteochondroma, but they are often more severe. Painless bumps can

  • arise at the site of tumor and pain and other discomforts can also take place if

  • pressure is put on the soft tissues, nerves, or blood vessels. Dysplasia

  • Epiphysealis Hemimelica or Trevor's disease and metachondromatosis are

  • considered differential diagnosis of both solitary and hereditary

  • osteochondromas. DEH is described as a type of over growth at one or more

  • epiphyses. Similar to osteochondroma, DEH is diagnosed prior to 15 years of

  • age and the growth of lesions end at puberty, when the growth plates close.

  • Metachondromatosis is a rare disorder that exhibit symptoms of both multiple

  • osteochondromas and enchondromas in children and is also inherited in

  • autosomal dominant mode. Treatment and prognosis

  • Osteochondromas are benign lesions and do not affect life expectancy. Complete

  • excision of osteochondroma is curative and the reoccurrences take place when

  • the removal of tumor is incomplete. Multiple reoccurrences in a well-excised

  • lesion indicate that it may be malignant. The risk of malignant

  • transformation takes place in 1–5% of individuals. If any symptoms of

  • cancerous tumor takes place, then the patient should be evaluated by a bone

  • specialist. No treatment is necessary for Solitary osteochondromas that are

  • asymptomatic. Treatments for solitary osteochondroma are careful observation

  • over time and taking regular x-rays to monitor any changes in the tumor. If the

  • lesion is causing pain with activity, nerve or vessel impingement, or if the

  • bone growth has fully matured and the presence of a large cartilage cap is

  • prominent, then it is advised that the tumor be surgically removed.

  • Osteochondromas have a low rate of malignancy (

Osteochondromas or osteocartilaginous exostoses are the most common benign

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骨軟骨腫 (Osteochondroma)

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    lhy2010 に公開 2021 年 01 月 14 日
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