Craniofacial fibrous dysplasia with cystic degeneration – A diagnostic challenge

Benign fibro-osseous lesions with cystic degenerations have been scarcely reported in craniofacial bones and its unusual characteristics pose a diagnostic challenge. Here, we report a case of craniofacial fibrous dysplasia presenting a large cystic degeneration. A 55-year-old woman had a history of pain, slight asymmetry on the zygomatic region and ocular pressure. Computed tomography revealed on the right side, multiple craniofacial bones showing a ground glass aspect, associated with an extensive hypodense, unilocular, well circumscribed lesion in the maxilla, and smaller lesions in the sphenoid bone. After a surgical procedure performed in another service, there was a complete improvement in symptoms, and after 1 year, the patient remains stable, with no changes. In the literature review, thirty-three reported cases of the same association in the craniofacial region were found. The main symptoms were sudden increase in the lesion and pain, and the indication of intervention in cystic lesions was only indicated in symptomatic cases or functional deficit. The knowledge of the possibility of the association of benign fibro-osseous lesions and cystic degenerations in craniofacial bones is essential to perform a correct diagnosis and treatment for these patients, consequently avoiding unnecessary procedures. Key words:Craniofacial fibrous dysplasia, Fibrous dysplasia, Benign fibro-osseous lesions, Cystic degeneration.


Introduction
Benign fibro-osseous lesions constitute a group of diseases, in which healthy bone is replaced by fibrous tissue with foci of bone neoformation.The 3 most common lesions affecting craniofacial bones are fibrous dysplasia (FD), cemento-osseous dysplasia (COD), and ossifying fibroma (OF).Although, such diseases differ clinically and radiographically , they present similar histopathological features (1).
FD is caused by a post-zygotic mutation in the GNAS 1 gene that is linked to changes in osteoprogenitor cells, leading to abnormal bone formation.Monostotic FD affects only one bone and polyostotic several bones and may be associated with syndromes, such as McCune-Albright.The term craniofacial FD is used for FD involving multiple skull bones (1)(2)(3).There are few reports showing cystic degenerations in benign fibro-osseous lesions.These lesions include aneurysmatic bone e782 cyst (ABC), simple bone cyst (SBC), and nonspecific cystic degeneration (CD) (4)(5)(6)(7).Due the scarcity of data considering benign fibro-osseous lesions and cystic formations in craniofacial bones, the diagnosis may be a challenge for clinicians and radiologists.According to our knowledge, a total of 30 cases of FD in craniofacial bones presenting cystic formations have been reported in the English language literature (1980-2020), and here we present a new case of FD presenting nonspecific cystic degenerations.

Case Report
A 55-year-old woman was referred to the Stomatology Department for evaluation of an injury on the right maxilla.During anamnesis, the patient reported to be treated and followed for 5 years by either otorhinolaryngologist and maxillofacial surgeon.She also had a history of pain and eye pressure, on the right side of the face, that ameliorated after a surgical procedure.In fact, the surgeon informed us that he found an empty cavity during the exploratory surgery.Due to doubts in relation to diagnosis, he referred the patient for our evaluation.On clinical examination, it was observed a slight swelling on the right side of the face.Computed tomography (CT) performed 6 years ago showed an extensive and expansive lesion with a mixed aspect mainly "ground glass".The lesion involved the maxilla, greater sphenoid wing, temporal, frontal, pterygoid process, floor and lateral wall Fig. 1: Computed tomography (CT) performed 6 years ago showed an extensive and expansive lesion with a mixed aspect such as "ground glass".The lesion involved the maxilla, greater sphenoid wing, temporal, frontal, pterygoid process, floor and lateral wall of the orbit of the right side.It was also observed an extensive hypodense and unilocular area in the right maxilla, which caused a remodeling of the lateral and inferior walls of the ipsilateral maxillary sinus, decreasing its dimensions.Moreover, a cortical thickening of orbital floor and anterior wall of the maxillary sinus was observed.Similar lesions (in smaller size) were also observed in the sphenoid bone.
of the orbit, all on in the right side.It was also observed an extensive hypodense, unilocular, well circumscribed lesion in the maxilla.Such lesion caused a remodeling of the lateral and inferior walls of the ipsilateral maxillary sinus, decreasing its dimensions.Moreover, a cortical thickening of orbital floor and anterior wall of the maxillary sinus was observed.It is worth mentioning that similar lesions, but smaller, were also observed in the sphenoid bone (Fig. 1).In the CT after the surgical procedure, there was no relevant alterations in the radiographic features when compared to the previous exams, except the continuity solution in the maxilla, compatible with the surgical procedure performed (Fig. 2).According to both clinical and radiographic features, the diagnosis of craniofacial fibrous dysplasia associated with cystic degenerations was established.In the CT control after one year, there are no changes, the patient is asymptomatic (Fig. 3).

Discussion
The association between craniofacial FD and cystic formations is uncommon, with few cases reported in the literature.The exact pathogenesis of this association is unknown.El Deeb (8) and Wojno & McCarthy (7) suggested that benign fibro-osseous lesions can lead to vascular and hemodynamic changes and deficient bone structural support favoring cystic formations.According to Ferreti (5) cystic lesions arise due to an intraosseous vascular defect, causing intramedullary hemorrhage.If e783 Fig. 2: CT performed after the surgical procedure, there was no relevant alterations in the radiographic features when compared to the previous exams (Fig. 1), except for an area which corresponds to the surgical access (red arrow).direct communication occurs with the bleeding region, an aneurysmatic bone cyst is formed, but a complete interruption of blood supply leads to the formation of a simple bone cyst.A previous study of our group (9) reported a series of cases of the association between SBC and benign fibro-osseous lesions, and one particular associated with FD in the mandible.It is accepted that the mandible is more commonly affected due to less vascularized bone, facilitating osteocyte death and cys-tic formations.In a retrospective study conducted at the Chang Gung Craniofacial Center, 9 out of 113 cases of craniofacial FD were associated with cystic degeneration, more commonly in the sphenoid bone.The authors did not find a clear predisposing evidence for cystic degenerations (4) occur.We found a total of 33 cases of FD presenting with cystic formations (SBC, ABC and CD) in craniofacial bones in the English literature ( There is no reported case in the literature of an association between FD and SBC affecting the maxilla, in our knowledge. Regarding treatment, it is suggested that symptomatic patients and/or presenting functional deficit, the cystic lesions should be promptly treated, otherwise the patient should be only followed up.Hong et al. (10) reported a case of a patient with FD and cystic degeneration affecting both mandible and maxilla.The patient had mandible pain, which was ameliorated after cystic assessment, with no further interventions.In our case, the surgical intervention, with cystic decompression, caused improvement of the ocular pressure and pain.
The patient remains stable, without symptoms.Current CT has showed no further alterations in the lesions.The patient is under follow-up and no surgical interventions has been indicated.
In conclusion, the present study described a rare case of craniofacial fibrous dysplasia with cystic degeneration.
To our knowledge, this is the third case of such associa-e786 tion in the maxilla.The knowledge of the association of benign fibro-osseous lesions and cystic degenerations in craniofacial bones is essential, considering that in most of the cases the treatment is expectant or performing only cystic decompression, and large resection must be avoided.

Fig. 3 :
Fig. 3: CT performed one year after the surgical procedure, the exam shows similar features.

Table 1 :
Cases reported in the literature of fibrous dysplasia in craniofacial bones associated with cystic formations.

Table 1 cont . :
Cases reported in the literature of fibrous dysplasia in craniofacial bones associated with cystic formations.