Subungual Warts, also known as exostoses, are one of the common bone tumors in clinical practice.
2 Disease nameSubungual osteochondroma
3 English namesolitary osteochondroma
4 Alias of subungual osteochondromasolitary osteochondroma; exophytic osteochondroma
5 ClassificationOncology > Bone tumors > Benign bone tumors > Benign bone tumors > Chondrogenic tumors > Osteochondroma
6 ICD number
M9210/1, D16
7 EtiologyThe exact etiology is unknown. Some consider osteochondroma to be a true tumor; others consider it to be a developmental epiphyseal growth deficiency.
8 Pathogenesis 8.1 Gross examinationOsteochondromas can vary greatly in size, generally located in the long tubular bone, the maximum diameter of the osteochondroma, on average, 4 cm, in the flat bone or irregular bone is usually larger, the largest individual report of 40 cm. with the tip of the osteochondroma in the shape of a tube or conical, the surface is smooth or knotted, and the shape of its top is not the same. Non-tipped osteochondromas are saucer-shaped, hemispherical or cauliflower-shaped. The tumor shows three typical layers in the section: (1) the superficial layer is a sparsely vascularized collagenous connective tissue that articulates with the surrounding periosteum and is tightly adherent to the tissues beneath it. The middle layer is a gray-blue hyaline cartilage, the cartilage cap, similar to normal cartilage, usually a few millimeters thick, and its thickness depends on the patient's age. In children and adolescents, who are in the active phase of bone growth, the cartilage can be up to 3 cm thick, while in adults, the cartilage cap is sometimes completely absent. This phenomenon is due to the pressure and wear and tear on the cartilage cap caused by the structures surrounding the tumor after growth has stopped. In adults, if the cartilage cap is more than 1cm thick, the possibility of malignant transformation of osteochondroma should be considered. In the case of non-tibial osteochondroma, the area occupied by the cartilage layer is larger. ③ The grass-roots level is the main body of the tumor, containing the cancellous matrix of the yellow marrow, which is connected to the affected bone.
In the section of a solitary osteochondroma, the cartilaginous cap is underneath the cancellous bone, with irregular reticulation and yellow marrow, and may also have red marrow. Islands of cartilage may protrude short distances from the surface of the osteochondroma or may be contained within the osteochondroma, and over time both now show marked calcification and/or ossification into yellowish-white dots that are hard and gravelly.
The periosteum covers the entire osteochondroma from the metaphysis to the cartilage cap and is adherent to the cartilage cap. Synovial fluid sacs, sometimes with pseudosynovium, may be seen at the top of the osteochondroma.
8.2 Microscopic examinationThe main purpose is to examine the cartilaginous cap of the osteochondroma, which is histologically similar to the epiphyseal growth plate. It can be seen as follows: ① In young patients with active tumor growth, most of the binucleated chondrocytes can be seen (Figure 1). ② When tumor growth stops, chondrocytes stop proliferating and degenerative changes occur. (iii) When the cartilage layer is occasionally disturbed by growth, calcium debris can be deposited in the cartilage. ④ When the tumor becomes malignant as chondrosarcoma, there is also significant calcification and ossification, and the chondrocytes have atypical nuclei.
9 Clinical manifestations of subungual osteochondromaMost solitary osteochondromas are often found in children or adolescents, and about 70% to 80% of patients occur under the age of 20. Because solitary osteochondromas do not become symptomatic until they have grown to a significant size, they are rarely seen before the age of 8 to 10 years. Because it grows similarly to bone, it reaches its maximum size around puberty, so most cases of solitary osteochondroma become symptomatic between the ages of 10 and 18.
The age factor is of diagnostic and prognostic importance. Prior to puberty, the growth of solitary osteochondromas is normal and it is virtually impossible for a peripheral chondrosarcoma to develop. In contrast, if a solitary osteochondroma recommences growth in adulthood, it has almost certainly transformed into a chondrosarcoma.
9.1 Symptoms and signsA hard, gradually growing mass without conscious pain or tenderness is the clinical hallmark. Slightly larger tumors are sometimes seen as a protuberance under the skin. When the tumor is too large, or due to the special anatomical site, it can produce corresponding clinical symptoms and signs. For example, a fracture at the base of the tumor can cause pain and swelling. Subungual osteochondromas originate from and are attached to the bony planes without adhesion to the soft tissues. Some cases of solitary osteochondroma are completely asymptomatic and may be detected on imaging for other reasons. A solitary osteochondroma may rub against overlying structures such as muscles, tendon membranes, and tendons, forming synovial cysts on their surfaces.
9.2 Sites of predilectionOsteochondromas can arise in any bone with endogenous cartilage ossification. In long tubular bones, especially in the femur (30%), humerus (20%), and tibia (17%) are the most frequent sites. It is less common in certain long tubular bones such as the radius and ulna. The lower limbs are more affected than the upper limbs, with a ratio of 2:1. Typical sites of development in long tubular bones are the epiphyses, rarely the diaphysis or epiphyses, and if they do occur, it may be another disease, Trevor's disease. Osteochondromas occur in the fast-growing areas of long tubular bone, such as the distal femoral epiphysis, humerus, tibia, and proximal fibula epiphysis.
It develops in about 10% of the small bones of the hand and foot and 5% of the ilium. Spinal incidence is less frequent (<2%), but is often noted for compression of the spinal cord. In the spine osteochondromas develop favorably on the appendages of the spine, especially on the spinous processes. It is common in the lumbar and cervical spine. Osteochondromas of the scapula occur in about 4% of cases and are often located on the front of the scapula and can produce pain and popping during movement. Osteochondroma occurring in the scapula can sometimes be misdiagnosed as a nodule in the lung when chest radiographs are taken.
10 Complications of subungual osteochondromaThe majority of osteochondromas have mild clinical symptoms and signs. In a few patients, the tumor can be spontaneously absorbed in childhood and adolescence, and the tumor disappears. The reason for this is that in some patients, osteochondroma fractures occur, and the tumor is absorbed due to active bone resorption; it may also be that the tumor gradually merges into the enlarged epiphyseal bone during growth and development. However, the following comorbidities can also occur during development.
10.1 FracturesUncommon, often occurring in large, pedunculated osteochondromas as a result of injury. However, delayed healing or non-healing rarely occurs. In individual patients the tumor disappears after fracture.
10.2 Bone deformitiesOsteochondromas cause three bone deformities: (1) poor canalization of the bone; (2) widening of the epiphysis; and (3) deformity of the surrounding bone. The latter often occurs when the osteochondroma is located in one of the two neighboring bones with close anatomical relationship. It is common for osteochondromas on the tibia to exert pressure on the fibula, resulting in fibular deformity.
10.3 Vascular InjuryOsteochondromas located near the knee joint can often cause vascular dislocation, and more serious complications such as arterial and venous ingrowth or the formation of pseudoaneurysms are rare comorbidities, but have been reported. It is common in males at an age when normal bone growth has nearly ceased. As the protective cartilaginous cap of the osteochondroma loses its luster, allowing blood vessels to rub against the non-smooth cartilaginous cap, the pulsation of the arteries and joint movements cause repetitive damage to the vessel walls, and eventually pseudoaneurysms are formed. Almost all osteochondromas combined with pseudoaneurysms occur at the proximal end of the popliteal artery. There are two reasons for this: ① The lower end of the femur and the upper end of the tibia are the most common sites. The proximal end of the popliteal artery is immobilized as it passes through the vastus medialis muscle, and the distal end of this artery is also immobilized by its anterior and posterior tibial artery branches. The distal and proximal ends of the popliteal artery have no mobility and thus show bowstring-like tension on the surface of the tumor. Pseudoaneurysms caused by osteochondromas are pulsatile soft tissue masses with altered arterial pulsation at their distal ends, but the diagnosis is confirmed by angiography.
10.4 Nerve damageThis comorbidity is rare. It produces different types of clinical symptoms depending on the site of origin.
10.5 Bursal cyst formationA bursal cyst forms around the tip of an osteochondroma. This usually occurs when the osteochondroma is large and the affected bone is highly mobile, such as the scapula or distal femur.
10.6 MalignancyMalignancy occurs in approximately 1% of patients. Osteochondroma malignant transformation can appear pain, swelling, soft tissue mass and other symptoms; X-ray can see the original stable osteochondroma grow again. Bone destruction, calcification irregularity and other manifestations.
11 Diagnosis of subungual osteochondromaBased on the history, age, clinical manifestations, site of incidence, X-ray examination, can be clearly diagnosed.
11.1 X-ray examinationThe diagnostic feature of a solitary osteochondroma is that the cortex of the host bone turns outward like the fingers of a glove, forming the cortical bone of the osteochondroma, and the cancellous bone is directly continuous with the cancellous bone of the epiphysis. Thus, osteochondroma is a redundant mass of bone, consisting of (i) a thin outer layer of cortical bone, (ii) an inner layer of cancellous bone, and (iii) a swollen, uneven apex. The boundary between a solitary osteochondroma and soft tissue is well defined. The internal structure of single osteochondroma is mature cancellous bone, but its pressure line is neither regular nor orderly, and sometimes it can be wide and irregular mesh-like cancellous bone. Osteochondromas are variable in shape and size. When an osteochondroma is tipped, it is often oriented toward the side of the diaphysis and away from the epiphysis.
The radiographic features of an osteochondroma are a bony protrusion on the bony surface of a long tubular bone, attached to the epiphysis, and composed of bone cortex and bone cancellous. Due to the different shapes of the tumor base, it can often be divided into two types: referred (with a narrow stem and wider at the top) and unattached (with a wide and flat base). Osteochondromas often occur in the epiphyseal area where the tendon ligaments attach. Its growth is often in the direction of the forces exerted by the tendons and ligaments, e.g., from the epiphysis to the diaphysis of the same bone. The top of the tumor is covered by cartilage, called cartilage cap, which varies in thickness, with the thin ones showing only a linear transparent area, which is not easy to be seen, and the thick ones showing a dense cauliflower-like shadow. If the cap is small, clearly demarcated, with regular punctate calcification, this manifestation is benign growth. If the cap is large and thick, with unclear boundaries, containing irregular or incomplete calcifications, attention should be paid to the possibility of malignant changes.
When osteochondromas are in the iliac region, they are often large, can form a large soft tissue mass, and can push and displace surrounding structures. The type of calcification is variable and often irregular. Identifying the tumor as benign or with malignant changes is difficult at this point.
Osteochondromas on the small bones of the hands and feet have an X-ray appearance similar to that of long tubular bones. Of note, small osteochondromas may be present in the terminal phalanges of the fingers and digits and are referred to as solitary osteochondromas (Figure 2).
11.2 Other Imaging TechniquesPlain X-rays of most subacromial bone warts are adequate for diagnosis and treatment. However, CT examination is often needed to help with more complex anatomy, such as the scapula, pelvis, spine and so on. For osteochondroma of long tubular bone, CT examination can provide the relationship between the tumor and the affected bone, the type of lesion matrix, calcification, and the thickness of the cartilage cap, which will be helpful in the differential diagnosis of osteochondroma or periosteal chondrosarcoma.
11.3 Differential diagnosisThe diagnosis can be made on clinical and imaging grounds alone, with the only problem being distinguishing benign osteochondromas from osteochondromas with sarcomatous transformation. Sometimes it is necessary to differentiate from calcification (ossification) of tendon attachments and parosteal osteoma. A thorough analysis of all clinical, radiographic, bone scan, gross pathologic, and histologic features is required.
12 Treatment of subungual osteochondromaMost cases of solitary osteochondroma do not require surgical resection, but should be closely observed, and the patient can carry out normal work and life. If the patient has pain in the area when moving, or if the area has grown, surgery should be done to remove it. When a single osteochondroma is located in the trunk bone, it can be removed even if it is asymptomatic to prevent the occurrence of chondrosarcomatous transformation which is not rare.
In addition to the above, surgery is indicated only when cosmetic or symptomatic. As with all malignant tumors, surgery for single osteochondromas is best not performed in childhood, for the reasons that it is difficult to determine the indications for surgery until the osteochondroma is fully grown, and that removal of a single osteochondroma in childhood can lead to local recurrence. However, in rare cases, such as when the osteochondroma causes considerable dysfunction and deformity, or when the growth is in the vicinity of a neurovascular bundle, it may be operated on in childhood.
Surgery for a single osteochondroma necessitates removal of the entire osteochondroma and its envelope (marginal resection) to avoid leaving a portion of the cartilaginous cap behind that can grow again. In adults there is no need to remove the stem and base of a solitary osteochondroma from the root because the bony portion of a solitary osteochondroma has no proliferative potential, and even intracapsular removal of the top of the osteochondroma will not recur. In children, surgical resection must be extracapsular, and the base and surrounding periosteum of the osteochondroma must be removed as well, because chondrogenic embryos with growth potential may be present in them, leading to postoperative recurrence. It is important to avoid stripping the periosteum from the cartilaginous surface of a solitary osteochondroma and to prevent fragmentation of the osteochondroma intraoperatively.
During surgery, the tumor should be fully exposed and the periosteum, cartilage cap, bone cortex and normal bone around the base should be removed. It is easy to remove the periosteum on the surface of the tumor and the normal bone around the base of the tumor too little during the surgery, leaving behind a protrusion of bone. Surgical resection is complete, and generally no recurrence. In the case of solitary osteochondroma, although the surgery is small, it should be completely resected, otherwise it is easy to recur.
If single osteochondroma is suspected to be malignant, it should be examined by nuclide scanning and CT in time, but it is often difficult to make a qualitative diagnosis by the above two examinations, so it should be excised completely at an early stage, and the diagnosis should be determined according to the histological examination at last.
13 PrognosisSurgical resection is effective and generally does not recur. Single osteochondroma, complete resection, otherwise prone to recurrence.
14 Prevention of subungual osteochondromaNo information available.
15 Related drugsCollagen
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