Fibro-osseous lesions are characterized by the replacement of normal bone with benign connective tissue that contains varying amounts of mineralized material [1]. These lesions are conventionally classified into three categories: 1) fibrous dysplasia (FD), 2) ossifying fibroma (OF), and 3) osseous dysplasia [2]. Although these entities share overlapping histopathological features, they differ in biological behavior, clinical course, and treatment considerations. Among them, FD and OF represent the two most common forms of benign fibro-osseous lesions. Nevertheless, both entities occur infrequently within the sinonasal tract [3,4]. Furthermore, fibro-osseous lesions arising from the nasal turbinates are exceedingly rare [3,4]. In this context, we report one case of FD involving the inferior turbinate and one case of OF involving the middle turbinate, both of which were managed by endoscopic endonasal surgery.

The two main categories of benign fibro-osseous lesions are OF and FD. FD accounts for approximately 7.5% of benign bone neoplasms [2,7]. Two principal clinical forms are recognized: monostotic (75%–80%) and polyostotic (20%–25%) [7,8]. The polyostotic form may be associated with café-au-lait spots and hyperfunctional endocrinopathies, a constellation referred to as McCune–Albright syndrome [8,9]. Craniofacial involvement is observed in approximately 50% to 100% of patients with polyostotic disease and in 10% to 30% of those with monostotic disease [8]. Within the craniofacial skeleton, FD most frequently affects the maxilla and mandible, followed by the frontal, parietal, and occipital bones [10]. In contrast, OF primarily involves the facial bones (85%), with the mandible representing the most commonly affected site (77%) [11]. The mean age at diagnosis ranges from 20 to 40 years, with a recognized female predominance [11,12]. Sinonasal involvement remains rare. OF is characteristically a locally aggressive and expansile tumor; therefore, complete surgical resection is generally required [11–13]. Previously reported fibro-osseous lesions involving the nasal turbinates are summarized in Table 1, including turbinate site, pathology, surgical approach, extent of resection, outcome, and follow-up.

Diagnostic considerations and potential pitfalls warrant emphasis, as fibro-osseous lesions of the turbinates may clinically resemble more common conditions such as turbinate hypertrophy or chronic inflammatory disease. Features including asymmetric turbinate enlargement, firm bony consistency, a progressive clinical course, and CT evidence of bony expansion or remodeling should be considered when differentiating fibro-osseous lesions from other etiologies [4]. On CT imaging, OF typically demonstrates a well-circumscribed and sharply defined margin, a characteristic that is generally absent in FD [12,13]. Both lesions are usually isodense; however, radiographic density may vary depending on the relative proportions of mineralized bone and fibrous tissue within the lesion [7,10].

However, because of overlapping histological and radiological characteristics, distinguishing between FD and OF remains diagnostically challenging [13]. Toyosawa et al. [14] performed immunohistochemical and molecular analyses and reported that osteocalcin immunoreactivity was strong throughout the calcified regions in FD but weak in OF lesions. In addition, polymerase chain reaction analysis demonstrated GNAS1 mutations in FD, whereas such mutations were absent in OF. Based on these findings, the authors concluded that immunohistochemical and molecular analyses are useful adjunctive tools for differentiating FD from OF. These observations support accumulating evidence that FD represents a non-inherited genetic condition caused by a sporadic missense mutation of the GNAS1 gene on chromosome 20, which encodes the alpha subunit of the stimulatory G protein (Gsα). This mutation leads to inhibition of GTPase activity and constitutive activation of adenylate cyclase–protein kinase A signaling pathways [14,15].

Management strategies for fibro-osseous lesions of the sinonasal cavity vary according to the biological behavior of each entity. FD is typically slow-growing and often stabilizes after skeletal maturity; therefore, asymptomatic and non-deforming lesions may be managed conservatively with periodic endoscopic and radiological surveillance [16]. Surgical intervention is generally reserved for patients with persistent symptoms, recurrent infection, cosmetic deformity, or functional impairment such as nasal obstruction [17]. In FD, conservative contouring or limited debulking is usually preferred to preserve normal anatomy, as the lesion lacks a clear boundary and aggressive resection may result in unnecessary morbidity [18]. For symptomatic FD, medical therapies such as bisphosphonates may be considered for the alleviation of bone pain, although their impact on lesion progression remains limited. More recently, denosumab has shown promise in reducing bone turnover and pain in FD patients who are unresponsive to bisphosphonates [16]. Treatment approaches may also be tailored according to patient age and growth status. In pediatric patients, active bone growth and higher recurrence rates favor a conservative surgical approach, with intervention reserved for severe symptoms or functional compromise. In contrast, adult patients may benefit from more definitive surgical procedures, including contouring or resection, particularly when addressing cosmetic deformity or functional deficits [16,17].

In contrast, OF behaves as a well-demarcated and expansile lesion with the potential for progressive growth. Owing to its discrete borders, complete surgical excision is considered the treatment of choice to minimize the risk of recurrence [19]. Endoscopic endonasal surgery is appropriate when the lesion is confined to the turbinate or lateral nasal wall without invasion of adjacent structures, whereas open approaches may be necessary in cases of extensive disease or involvement of the orbit or skull base [20].

Although rare, malignant transformation has been reported in both FD and OF. FD undergoes malignant change in fewer than 1% of cases, most commonly resulting in osteosarcoma, fibrosarcoma, or chondrosarcoma. Similarly, OF has rarely been reported to transform into malignant entities such as osteosarcoma [21,22]. Regardless of lesion type, long-term surveillance is recommended, as FD carries a small but recognized risk of malignant transformation and OF has a documented, albeit low, recurrence rate following incomplete excision [23]. These considerations underscore the importance of individualized management and sustained follow-up in patients with turbinate fibro-osseous lesions.

When managing fibro-osseous lesions of the nasal turbinates, several operative considerations are essential to achieving complete resection while minimizing morbidity. Preoperative CT evaluation is critical for delineating lesion boundaries and identifying key anatomical landmarks, including the basal lamella, skull base height, lamina papyracea, and the relationship of the turbinate to the nasolacrimal duct and ostiomeatal unit [24]. Because OF typically exhibits a well-circumscribed interface, en bloc resection can often be performed safely. In contrast, FD frequently demonstrates an ill-defined interface with native turbinate bone, necessitating a more conservative, piecemeal debulking strategy to avoid excessive tissue loss and functional compromise [19].

During surgery, meticulous preservation of the turbinate mucosa is particularly important. A subperiosteal elevation technique enables maintenance of a continuous mucosal layer, which in turn reduces crusting, accelerates postoperative healing, and lowers the risk of synechiae formation [25]. Functional preservation is especially critical in the inferior turbinate, where excessive resection may lead to altered airflow dynamics or the development of empty nose symptoms [26]. Although bleeding is usually minimal in both lesions, it should be carefully controlled using topical vasoconstrictors and judicious bipolar or suction cautery to prevent thermal injury to the preserved mucosa. Because fibro-osseous lesions may distort the normal anatomic configuration of the turbinate, surgeons must exercise particular caution near the skull base attachment, medial orbital wall, and frontal recess pathway to avoid inadvertent injury [27]. Another key consideration is the method of resection. In both of our cases, the lesions were removed using strong forceps without the need for drilling, thereby reducing thermal and vibrational trauma to adjacent structures. Nevertheless, excessive traction must be avoided, particularly in proximity to the basal lamella and skull base. Finally, postoperative measures, including the use of silastic stenting when indicated to reduce synechiae formation and the encouragement of early saline irrigation, play an essential role in mucosal recovery. When these principles are consistently applied, endoscopic endonasal surgery can provide excellent visualization, enable precise tumor removal, and avoid the morbidity associated with external surgical approaches [11].

This report has a limitation. Because molecular testing, such as GNAS1 mutation analysis, was not performed, molecular differentiation between the entities was not possible in our cases, and the diagnoses relied on clinical and radiological correlation in conjunction with histopathological evaluation [28].

In this report, we present a case of FD that was conservatively resected endoscopically without complications or recurrence after a 9-year follow-up, as well as a case of OF that was completely resected endoscopically without complications or recurrence after a 3-year follow-up. Based on these outcomes, endoscopic endonasal surgery should be considered the treatment of choice for fibro-osseous lesions that are amenable to endoscopic access and do not involve invasion of surrounding structures.