Aneurysmal bone cyst of the maxillary sinus secondary to fibrous dysplasia: Report of a rare case and review of the literature

ABC developing within FD in head and neck region is quite rare. Clinical presentation of FD and ABC depends on the location and scope of content. The majority of reported cases were seen in male children and adolescents. Complete excision of these lesions is the recommended treatment.This report is about a 27 year-old male patient who presented with a mass in hard palate treated with total excision. Correspondence to: Umur Yollu, Department of Otorhinolaryngology, Cerrahpasa Medical School, Istanbul University, Fatih, Istanbul, Turkey, Tel: +90 212 414 30 00, E-mail: umuryollu@hotmail.com Received: October 01, 2017; Accepted: October 23, 2017; Published: October 27, 2017 Introduction Fibrous Dysplasia (FD) is a benign skeletal disease in which medullary bone is replaced with fibrocellular tissue. It results from abnormal fibroblast development [1]. Aneurysmal Bone Cysts (ABC) are relatively rare, benign vascular lesions and also may exist secondary to the pathological bone lesions [2]. FD in combination ABC that appears as a symptomatic or asymptomatic mass is quite rare. Clinical presentation of FD and ABC depends on the location and scope of content. The majority of reported cases are seen in male children and adolescents. Complete excision of these lesions is recommended.


Introduction
Fibrous Dysplasia (FD) is a benign skeletal disease in which medullary bone is replaced with fibrocellular tissue. It results from abnormal fibroblast development [1]. Aneurysmal Bone Cysts (ABC) are relatively rare, benign vascular lesions and also may exist secondary to the pathological bone lesions [2].
FD in combination ABC that appears as a symptomatic or asymptomatic mass is quite rare. Clinical presentation of FD and ABC depends on the location and scope of content. The majority of reported cases are seen in male children and adolescents. Complete excision of these lesions is recommended.
Case report 27 year old male patient admitted to our clinic with complaints of swelling in hard palate and toothache. Medical history was unremarkable, and general health condition was well. On physical examination, a 4x5 cm soft mass was seen on the middle part of the hard palate. The overlying mucosa was intact and bony consistency of the hard palate could not be palpated. Nasal endoscopy was unremarkable.
Paranasal sinus CT scan revealedthat the lesion was originating from the inferior wall of the maxillary sinus and was surrounding the left posterior molar teeth. The central part of the lesion had soft tissue dansity, periferal areas had ground glass opacity and the nature of the lesion was expansile (Figure 1). Age and radiological findings of the patient were compatible with the fibrous dysplasia.
Caldwell-Luc antrostomy was performed and the lesion that filled the maxillary sinus and expanding to hard palate was totally excised with blunt dissection. Inferior antrostomy was done and stabilisated with a rubber drain. Histopathological examination was reported as aneurysmal bone cystsecondary to fibrous dysplasia with woven bone formation and short spindle cells within the stroma (Figures 2 and 3).

Literature review and discussion
Fibrous dysplasia which was first described by Lichtenstein [3] constitutes 2,5 % of all bone tumors and %7 of benign bone tumors [4]. It is often seen in young male patients. FD can present as monostotic (%70) or polystotic (%30) disease and may be a component of McCune-Albright syndrome [5]. At the craniofacial area; maxilla, mandible, frontal and temporal bones are the most frequent sites of ivolvement. CT images usually reveal extensive diploic spaces, enlargement and ground glass opacity of the affected bones and MRI shows typically low signal intensity on T1 and T2-weighted images [6].
ABC can be seen about 1.4% of all bone tumors but only 3-6% of them present in the cranium [7]. ABC mostly affect patients under under 20 years without gender difference [8]. Fluid-filled cavities are common and can be detected on CT or MR images [9]. On histopathologic examination; ABC present with blood-filled cavernous spaces which are usually seperated by fibrous tissue.
This report presents a case who was diagnosed as concominant FD and ABC. The occurance of ABC in combination with FD in the head and neck region is extremely rare. Up to date only several cases has been reported and most of these cases the disease is located on the skull base with only 3 cases of maxilla involvement. The cases of concomitant FD and ABC on the sinonasal region are summarized in Table 1 [10][11][12][13][14].
The presentation of these lesions depends on the sites of involvement, growth rate and anatomic structures of the involved region. Craniofacial lesions usually present with symptoms resulting Consistent with other reports the growth pattern of our case was slow without any compression over vital structures.
Diagnosis of FD combined with ABC depends on radiologic and pathologic findings. On radiology the typical appearance of FD     as ground glass opacity at the periphery of the lesion was detected on CT images combined with cystic soft tissue dansiy in the center. Intraoperative abundant bleeding rouse the suspect of ABC and postoperative definitive pathology confirmed the diagnosis ABC associated with FD. We believe that typical findings of FD combined with cystic spaces on CT images may be helpful in preoperative differential diagnosis and precautions about bleeding during surgery may be undertaken accordingly.
Optimal treatment of these lesions is total excision. Other treatment modalities are arterial embolization, sclerotherapy, cryotherapy, radiotherapy or combination of these methods but recent studies showed that radiotherapy alone has the risk of post-irradiation sarcoma [15]. In secondary ABC's, such as our case, the treatment plan should be set according to the site of primary lesion. Most of the reported cases (concomitant FD with ABC) treated with surgical excision and the results are quite good. We treated our case by total surgical excision. The lesions impingement symptoms and findings or patients with cosmetic problems should be treated by surgery and as fibrous dysplasia has a potential of malignant transformation (0.5% of patients with monostotic FD; 4% of patients with polystotic FD can develop malignant transformation) [16] the patients should be closely monitored. In our case after two years follow-up the patient is well without reccurence.
In conclusion although combination of FD and ABC is rare, awareness of such cases may lead preoperative suspect and preoperative and intraoperative precautions on bleeding from ABC.