Osteoma is a type of benign tumor commonly occurring in craniofacial structures such as the paranasal sinuses. It may be composed of either trabecular (spongy) bone, compact bone, or a combination of both.
Osteomas typically occur in the craniofacial structures, with the paranasal sinuses, mandible, or the calvarium (skull vault) being the most commonly affected.
Osteomas are generally asymptomatic except in some cases where they are located near structures that cause signs or symptoms when compressed by the tumor. Osteomas in the paranasal sinuses may cause facial asymmetry, mucocele formation, or sinusitis    . Osteomas arising from the orbital bones may lead to visual problems such as diplopia or amaurosis fugax and anatomic abnormalities including ptosis, lid edema, proptosis, or exophthalmos  . However, neurologic deficits may arise if the tumor extends intracranially to affect the brain or cranial nerves .
Osteomas are usually detected incidentally during imaging studies conducted for other reasons such as trauma . When osteomas produce symptoms, they can cause swelling, pain at the area of the tumor, deformities, or even pathologic fractures.
The typical appearance of osteomas is a round or oval, well-circumscribed, white or tan tumor covered by a thin layer of fibrous periosteum. Osteomas are attached to the underlying bone by either a broad base or a narrow stalk. Osteomas may also be associated with other conditions such as Gardner syndrome, especially when multiple tumors are present.
The most useful diagnostic tests for osteomas are imaging studies, with the plain radiograph being the most cost-effective. Ivory osteomas have a characteristic radiodense appearance in radiographs, whereas mature osteomas demonstrate a radiodense margin with a central hypodense marrow. Pathologic fractures caused by osteomas are readily detected through radiographs as well. The suspicion of malignancy in some lesions that are not clearly benign on X-ray examination may require advanced imaging techniques such as CT scans, magnetic resonance imaging (MRI), or scintigraphy.
Osteoid osteomas have a slightly different appearance from osteomas, having an intracortical nidus with varying degrees of calcification accompanied by bone marrow edema, cortical thickening, or sclerosis. However, these findings may be seen in other conditions such as arthritis, infections, or other tumors.
Osteomas generally do not require excision since they are benign and have very low potential for malignant transformation. However, tumors that cause significant complications due to mass effect, such as cosmetic or neurologic abnormalities, may require treatment. Excision of the tumor can be achieved through radiofrequency ablation or surgery. However, surgical removal is preferred over radiofrequency ablation if the tumor lies near the skin, nerves, or blood vessels since the heat produced by radio waves may damage these structures.
Osteoid osteomas generally cause night pain and can be treated by salicylates. Asymptomatic lesions do not require aggressive treatment and may be observed using regular X-ray examinations every 6 months. Recent evidence suggests that the use of NSAIDs may cause spontaneous resolution in certain groups of patients within 2-3 years .
Osteomas are benign tumors with no malignant transformation potential. Excision is not necessary except in some cases when they cause significant cosmetic damage, mass effect (i.e. impingement of a blood vessel or nerve), or complications such as mucocele formation. Recurrence of osteomas rarely occurs, even in tumors that are not completely excised.
The pathologic mechanism behind osteomas is poorly understood. Some theories regarding their etiology include a pathologic reaction against trauma or infection, a relationship to osteoblastoma, or a developmental anomaly. Other theories suggest that osteomas may also be a type of inflammatory reaction. Osteomas in the facial bones may be associated with Gardner syndrome.
Osteomas commonly occur between the fourth and fifth decades of life   but may affect all age groups with a slight male predilection. Osteomas of the paranasal sinuses are diagnosed incidentally and may appear in approximately 3% of computed tomography (CT) scans of the sinuses . Osteoid osteomas, on the other hand, are more prevalent in younger males between the ages of 10 to 35 and represent approximately 10% of all benign bone lesions .
Choroidal osteomas and osteoma cutis, in contrast, are more common in females. Multiple military osteoma cutis, characterized by numerous small osteomas affecting the face, is typically seen in middle-aged Caucasian women , whereas choroidal osteomas are associated with young white women . However, osteoma cutis may affect patients of all ages.
Osteomas may have variable composition and are classified according to the type of bone present in the tumor. Ivory osteomas, also known as eburnated osteomas, are the most common type  and are composed mainly of dense, compact bone without trabecular bone, Haversian canals, or fibrous components. Mature osteomas, on the other hand, are composed of dense and trabecular bone much like normal bone. They are also called osteoma spongiosum or trabecular osteomas due to the presence of spongy bone and marrow tissue in some cases. Mixed osteomas, as their name implies, comprise features of both ivory and mature osteomas.
The histological patterns of osteomas also vary according to where they are located. The fibrovascular component of osteomas arising from bone sutures is significantly reduced compared to osteomas arising from different areas .
There are no preventive measures against osteomas. However, they are slow-growing, benign tumors that do not have the potential to metastasize or become malignant. Most osteomas can be left untreated and do not cause symptoms or complications.
Osteomas are bone-forming (osteogenic) tumors whose growth is almost limited to membranous bones, especially the skull and craniofacial structures. However, they can also arise from other areas of the body such as the skin or soft tissues. Based on their origin, osteomas are classified as homoplastic if they arise from bone and heteroplastic if they arise from soft tissues.
Osteomas commonly grow from the paranasal sinuses and are usually diagnosed incidentally during routine imaging procedures. Another form of osteoma known as choroidal osteoma may occur in the choroid layer of the eyeball. Children and adolescents are more prone to develop osteoid osteomas, which are tumors arising from bones of the skull. These types of osteomas usually cause night pain that can be relieved with salicylates.
An example of heteroplastic osteoma is osteoma cutis, which is the presence of bone tissue in the skin that is not due to mechanisms that cause cutaneous ossification such as trauma, neoplasms, or inflammation .
Osteomas are benign and do not have the potential to become malignant. They can be left untreated unless they cause significant symptoms or disability, such as obstruction of the paranasal sinuses or compression of the structures of the central nervous system.
Osteomas are benign tumors arising from membranous or flat bones such as the skull and the bones inside the nasal cavity. They can also grow from soft tissues such as the skin and a layer of the eyeball known as the choroid (choroidal osteoma). Osteomas are slow-growing, non-malignant tumors that generally do not cause symptoms and are usually detected only during X-rays or scans performed for different reasons.
Osteomas generally affect people in theirs 30's or 40's, especially males. However, another form of osteoma called osteoid osteoma commonly affects younger males. Osteomas arising from the skin (osteoma cutis) can affect individual of all ages. A form of osteoma producing numerous small osteomas on the skin of the face (multiple miliary osteoma cutis) affects middle-aged Caucasian women.
Osteomas can be left untreated unless they cause significant deformities or complications such as compression of an adjacent anatomical structure, for which they can be removed by surgery or a special procedure called radiofrequency ablation. Osteomas are not cancerous and will not spread to other parts of the body. Surgical removal of the tumor is often enough to relieve the pain caused by the tumor. However, analgesics or NSAIDs can be taken by patients who do not prefer to undergo surgery.