Ⅰ. INTRODUCTION

Vascular malformation is one of the representative vascular diseases that occurs in the oral and maxillofacial region, along with hemangioma.¹⁾ Most vascular malformations do not cause symptoms until they are induced by a specific event, including puberty, pregnancy, surgery, or trauma.²⁾ Among them, intraosseous vascular malformation (IVM) is a benign and slowly growing vascular lesion formed in the bone and presents as a vascular abnormality or vascular proliferation.³⁾

Previously, IVM has been mistakenly referred to as “intraosseous hemangioma” to describe both vascular malformations and tumors located within the bone structure.⁴⁾ Therefore, IVM is considered rare, but the actual incidence is difficult to calculate accurately given the historical use of various terms and has been reported to account for approximately 1% of neoplasms of the bone ^{5, 6)} IVM is an abnormal development of blood vessels that occur in the bone, most commonly in the vertical column and calvarium, and rarely invade the facial skeleton.^6-9) Symptoms of IVM of the oral and maxillofacial region include facial asymmetry, headache and visual disturbance.

IVM is difficult to diagnose accurately due to its non-specific clinical aspects and lack of characteristic imaging findings. In addition, because the incidence of vascular malformations in the oral and maxillofacial region is low, a false or delay diagnosis is likely, hindering prompt and appropriate treatment. Therefore, histopathological examination of the suspected lesion is essential, and the characteristics of vascular malformations and hemangiomas that distinguish them from other diseases of vascular origin must be accurately recognized.

In this case report, we present a rare case of IVM occurring in the maxilla, along with a literature review.

Ⅱ. CASE REPORT

An 18-year-old female patient was referred to the Department of Oral and Maxillofacial Surgery of Seoul National University Dental Hospital with the chief complaint of a radio-opaque mass in the upper right maxilla. Biopsy for pathological diagnosis of the lesion was attempted at a local dental hospital before visiting our hospital. However, it could not be completed due to severe intraoperative bleeding. In the clinical examination during the first visit to our hospital, the patient exhibited right facial swelling without pain or discomfort. Computed tomography (CT) images revealed a bone-forming lesion with a fine bone trabecular pattern in the right maxilla, growth of which was pressing on the surrounding cortical bone. The margins of the lesion exhibited a pattern of very hazy dysplastic bone with smooth margins (Fig. 1). Infraorbital nerve mapping was performed to assess neurosensory disturbance due to the lesion and showed symmetric normal sensory function on the affected side compared to the non-affected side. An open biopsy was planned under general anesthesia for histopathological examination of the lesion. After performing a 1.5-cm vestibular incision above the right upper lateral incisor and canine, a mucoperiosteal flap was elevated carefully above the lesion. During excision of part of the lesion, high vascularity with a relatively large amount of bleeding was observed (Fig. 2).

Histopathological examination of the specimen revealed IVM, with numerous vascular structures and fibrous connective tissue within the bone matrix (Fig. 3). In immunohistochemistry, SMA and CD31 staining was performed to assess the smooth muscle and vascular endothelial cells of the vascular wall cells, and the presence of numerous vascular structures within the bone matrix was confirmed.

Ⅲ. DISCUSSION

IVM is a rare disease in the oral and maxillofacial region and is difficult to treat due to the risk of excessive bleeding. Surgical procedures performed on the lesion or adjacent tissues without an accurate diagnosis of the lesion may cause persistent and extensive bleeding, and potentially life-threatening bleeding. Accurate differential diagnosis of hemangiomas and vascular malformation is essential for establishing a correct treatment plan. However, vascular malformations of the facial bone are difficult to diagnose because they are usually asymptomatic or have no characteristic radiological findings.

In the past, hemangioma and vascular malformations caused confusion in the use of the terms, but in 1982, Muliken and Glowacki pathologically classified the active proliferation of endothelial cells as hemangiomas and not as vascular malformations depending on the characteristics of the cells.³⁾ Hemangiomas are benign tumors caused by growth of vascular tissue, with most appearing at a young age but not at birth and growing rapidly in early childhood with gradual spontaneous dissolution.^10,11) Unlike hemangiomas, vascular malformations are present from birth and usually persist for a lifetime.¹⁰⁾ Although vascular malformations occur congenitally, they also can occur due to acquired causes such as trauma or changes in endogenous hormones resulting in hemodynamic activity and can occur iatrogenically.¹²⁾

The vascular malformations can be classified into lymphatic malformations, capillary-venous malformations, venous malformations, and arteriovenous malformations. Although the biological and clinical characteristics differ by type of vascular malformations, overall, vascular malformations usually do not regress and continue to expand over time. Among them, the present case showed the venous malformation as a result of histopathological examination, which is the most common type of low-flow vascular lesions and comprise up to two thirds of congenital vascular malformations.¹³⁾ Venous malformations consists of atypical venous vessels with various sizes and wall thicknesses.¹⁴⁾ Intraosseous venous malformations are commonly misdiagnosed as ‘bone hemangioma’, however osseous hemangioma is a very rare entity.¹⁵⁾ The typical appearance of the intraosseous venous malformations in the maxillofacial region is a bulging mass. They can rarely cause displacement, mobility or root resorption of involved or adjacent teeth, and asymmetry of the dental arches.^{16, 17)} Venous malformations may appear during puberty and pregnancy in female patients due to the estrogen-responsive nature of venous malformations, and may swell after several stimuli, such as trauma, thrombosis, of infection.

CT is the preferred imaging modality over magnetic resonance imaging (MRI) for intraosseous vascular malformations. Especially, CT scans of intraosseous venous malformations exhibit parallel radiopaque striations with altered trabecular patterns and osteolytic areas in the lesion, which is often described to have a ‘honeycomb’ appearance. However, the characteristic radiographic features of venous malformations can be similar to those of other pathologic lesions, such as osteosarcomas, osteoblastomas, myxomas, or fibrous dysplasia, that might confuse the diagnosis.^18,19) Thus, during the biopsy for diagnosis of the lesions having these characteristics, it is necessary to prepare for massive bleeding and perform the surgical procedures carefully with consideration of the possibility of vascular malformations. In the present study, the patient exhibited the typical radiographic features of venous malformations on CT images, and showed low-flow bleeding during the surgery, which was likely of oozing rather than arterial bleeding with high-flow. In addition, histopathologic examinations revealed large, widely venous channels with irregular shapes and sizes, consistent with the venous malformations.

There are various goals of treatment for IVM: elimination, hemorrhage control, and prevention of recurrence.¹⁸⁾ Elimination and prevention of recurrence could be achieved by surgically resecting the lesion. On the other hand, conservative hemorrhage control consists of transvenous or transarterial embolization, packing of bone wax to bone cavities with curettage, radiotherapy, and sclerotherapy. Endovascular embolization has been used prior to surgical treatment or has been used for obliteration of the malformation. Embolization alone is generally not recommended but could be helpful for patients who do not meet the requirements for surgical resection.²⁰⁾ Embolization is performed through placement of occlusive material directly into the core of the lesion. This can be achieved by direct transosseous venous puncture or transfemoral catheterization for delivery of embolic agents such as titanium micro- coils, polyvinyl alcohol, and N-butyl-2-cyanoacrylate glue.²¹⁾ Although these conservative treatment modalities can successfully control vascular malformations, bony deformity or effects on adjacent structures can be controlled and corrected only through surgical treatments.¹⁸⁾ In the present report, although surgical resection with or without embolization of afferent feeding vessels may be the definitive treatment for the lesion,²⁰⁾ the patient underwent only incisional biopsy due to personal choice and had no other complaints or symptoms except facial swelling. For younger patients, conservative treatments should be the first line treatment unless the patient requests for surgery, and surgical resection could be postponed until there recurrence after conservative treatment.

Ⅳ. CONCLUSION

This case report presented a patient referred for extensive bleeding during incisional biopsy for a lesion in the maxilla that was diagnosed with IVM and an associated literature review. To prevent life-threatening hemorrhage that can occur during surgical procedures, an understanding of the clinical, radiological, and pathological characteristics of IVM is necessary.