Osteoma

Osteoma is the most common benign tumor of the paranasal sinuses, with a reported incidence of 0.5% to 3% in the general population. These tumors are slow growing and are often discovered as an incidental finding. Although osteomas were previously thought to occur most often in the frontal sinus, a recent study found that 55% of these tumors were located in the ethmoid sinuses, followed by the frontal sinuses at 37.5%. Possibly because of their slow growth rate, most paranasal osteomas are asymptomatic and tend to only cause symptoms when they grow large enough to compress local structures or obstruct the sinus drainage pathways. Presenting symptoms can vary based on tumor location, but most frequently include frontal headache, facial pain, and chronic sinusitis. Less commonly, these tumors can lead to the development of a mucocele or erode nearby structures such as the orbit or cranium.

Because of their benign course, osteomas that are small and asymptomatic can be conservatively managed with observation. However, specific indications for surgical intervention have been proposed. Savic and Djeric recommended surgery for osteomas that are symptomatic, rapidly growing, obstructing the frontal recess, leading to rhinosinusitis, causing facial deformity, or extending beyond the frontal sinus ( Fig. 1 ). More recently, Chiu and colleagues proposed a frontal sinus osteoma grading system to guide decisions regarding appropriate surgical approach. Their system categorizes osteomas into 4 distinct grades based on 3 primary characteristics: the location of the base of attachment, anterior-posterior diameter of the lesion, and tumor location relative to a virtual sagittal plane through the lamina papyracea. Although their original recommendations for an endoscopic versus open approach based on these grades have been adjusted with subsequent endoscopic innovation, this grading system remains useful and is widely used in the literature.

Endoscopic drill-out of a frontal osteoma. ( A ) Sagittal image revealing an extensive frontal osteoma completely filling and obstructing the frontal outflow tract. ( B ) Progressive drill-out of the noted osteoma with access to the overlying frontal antrum allowing visualization of the margins of resection. ( C ) Postoperative imaging revealing subtotal resection of the noted osteoma with reestablishment of the frontal sinus outflow tract. Of note, because the patient presented with complications secondary to sinus obstruction, the goal of the procedure was to primarily reestablish a functional frontal sinus.

Inverted Papilloma

Inverted papillomas (IP) are benign tumors of the paranasal sinuses. The incidence of IP has been reported at 0.74 per 100,000/y, with 1% to 16% of these tumors originating in the frontal sinus ( Fig. 2 ). Overall, the most common site of origin for IP is the lateral nasal wall. In addition, there seems to be a male predominance for these tumors, with a male to female ratio of 3.3:1. IPs are typically treated with complete surgical resection because of their risk of recurrence without complete resection and potential to be locally destructive. Moreover, these lesions have the capacity to harbor or transform into squamous cell carcinoma (SCC). A recent meta-analysis of frontal sinus IP by Walgama and colleagues discovered that 4.1% included SCC on final histopathology. This study also found that IPs of the frontal sinus are found bilaterally in about 16% of cases, a rate that is considerably greater than IP in other locations. This difference may be caused by incomplete initial resections or an intrinsic inability of the frontal intersinus septum to serve as an effective barrier to spread. One additional challenge with the removal of IPs is their tendency to recur. Walgama and colleagues reported the rate of frontal sinus IP recurrence to be 22.4%, similar to previously reported rates of 22% and 16.7%. These concerning findings show the importance of ensuring a complete resection when choosing among potential surgical approaches ( Fig. 3 ).

Inverted papilloma imaging. ( A ) Coronal image revealing an extensive frontal inverted papilloma with appreciable hyperostosis about the roof of the frontal sinus. ( B ) Sagittal image revealing an extensive frontal inverted papilloma with appreciable hyperostosis about the posterior table. The noted hyperostosis indicates the region of tumor origin/attachment and should be evaluated when determining an appropriate approach.

Combined endoscopic and open approach to a frontal inverted papilloma. ( A ) Endoscopic approach and resection of the inverted papilloma with radiographic findings seen in Fig. 2 . Note that a Draf IIb has been performed, allowing wide access to the frontal sinus antrum. ( B ) Open approach to the noted frontal inverted papilloma via a unilateral osteoplastic flap affording access to the posterior table and roof of the frontal sinus to ensure these sites of origin are adequately addressed. ( C ) Endoscopic view of the combined approach with a gloved finger seen traversing the site of the osteoplastic flap.

Squamous Cell Carcinoma

SCC is by far the most common sinonasal malignancy and accounts for approximately 41% of such cancers. SCC occurs most frequently in the nasal cavity (46%) and maxillary sinus (40%), and least frequently in the frontal sinus. Because initial symptoms can be vague and easily mistaken for benign sinonasal disease, SCC is typically diagnosed at advanced stages, and lymphatic metastasis is present in 10% to 20% of patients at the time of diagnosis ( Fig. 4 ). Thus, SCC carries a poor overall prognosis, with a reported 5-year survival rate of 50% to 60%. Occupational exposures to wood dust, nickel, or formaldehyde have been widely reported as risk factors for the development of both SCC and other sinonasal cancers. These irritants may lead to carcinogenesis by eliciting chronic inflammation. In addition, human papillomavirus has been linked to sinonasal SCC via malignant transformation of inverted papilloma tumors. As with other sinonasal malignancies, surgical resection in adherence with oncologic principles with postoperative adjuvant therapies is the preferred mode of treatment. Depending on specific tumor extension and location, modern endoscopic approaches can effectively achieve complete resections of sinonasal SCC.

Sinonasal squamous cell carcinoma imaging. Axial image revealing an extensive frontal sinonasal squamous cell carcinoma with frontal transgression and dural extension with associated lateral dural enhancement.

Sinonasal Undifferentiated Carcinoma

Sinonasal undifferentiated carcinoma (SNUC) is a rare and highly aggressive neuroendocrine malignancy that was first described by Frierson and colleagues in 1986. The age-adjusted incidence is 0.02 per 100000, and there is a significant male predominance. SNUC often initially presents with vague symptoms that worsen with rapid tumor growth. A literature review by Xu and colleagues found that nasal obstruction, epistaxis, visual disturbances, and headache are the most common presenting symptoms. Previous studies have reported that most patients are diagnosed with advanced disease, with nearly 60% of patients having disease extending beyond the paranasal sinuses. Of those patients, 53% had orbital involvement, 41% had skull base involvement, and 13% had brain involvement. Distant metastasis to the neck, lungs, liver, and bone has also been reported. The long-term prognosis at the time of SNUC diagnosis is grim, with a reported median survival of 22.1 months and a 5-year survival of 34.9%. Because of this high mortality, SNUC has been treated with a variety of multimodal approaches, including aggressive surgical resection when possible plus adjuvant and/or induction chemotherapy and/or radiation. Further research is required to elucidate the optimum treatment regimen for these aggressive carcinomas.

Small Cell Neuroendocrine Carcinoma

Small cell neuroendocrine carcinomas (SNECs) are poorly differentiated, aggressive malignancies that predominantly occur in the lung. However, approximately 4% of SNECs occur in extrapulmonary sites, including the paranasal sinuses. Of note, all SNEC tumors share similar histologic features. Detailed morphologic and immunohistochemical analysis is crucial for accurate diagnosis and to distinguish these malignancies from other sinonasal neuroendocrine malignancies, namely SNUC and esthesioneuroblastoma. As with SNUC, patients with SNEC often present with advanced disease, in part because of similar, nonspecific presenting symptoms, such as epistaxis, nasal obstruction, and nasal discharge. Overall, because of a combination of late presentation and their shared characteristics with pulmonary SNEC, sinonasal SNECs may be reasonably treated first with a chemotherapy or radiotherapy regimen, with surgical intervention reserved primarily for nonresponders. Despite these interventions, the rates of local recurrence and metastasis are each approximately 30% and the 5-year survival is only 10%.

Esthesioneuroblastoma

Esthesioneuroblastoma (ENB), also referred to as olfactory neuroblastoma, is a sinonasal neoplasm that is thought to originate from the olfactory neuroepithelium of the superior nasal cavity. ENB is rare and accounts for 3% to 6% of sinonasal malignancies. Although it was previously thought to be a low-grade malignancy, it is now known that ENB commonly invades local structures, including the paranasal sinuses, cranial vault, and orbit, and has a propensity for distant metastases. As with the previously discussed SNEC and SNUC, proper histology and immunologic analysis are crucial to avoiding misdiagnosis, which can lead to selection of inappropriate treatment plans. Cohen and colleagues showed this potential hazard after reviewing previously diagnosed ENB at their institution and finding that 10 out of 12 of these tumors carried an incorrect diagnosis. The rarity of this tumor has largely limited the literature to retrospective studies and an ideal treatment method has been difficult to elucidate. In the past, a craniofacial resection with adjuvant radiation was the gold standard of treatment, but endoscopic resection is now possible and preferred for certain patients in whom proper oncological principles are feasible. A large meta-analysis by Devaiah and Andreoli found no difference in survival rate between surgical approaches, a finding also corroborated by Tajudeen and colleagues. Overall, the combined approach of surgical resection with radiotherapy and possible chemotherapy seems to be the appropriate treatment modality for most patients with ENB. Of note, ENB tumors have shown a prolonged time to both local recurrence and distant metastasis, and proper management necessitates long-term follow-up for periods even greater than 10 years.

Sinonasal Non-Hodgkin Lymphoma

Mature B-cell non-Hodgkin lymphoma (NHL), which includes diffuse large B-cell NHL, is the second most common sinonasal malignancy after SCC. As a group, these tumors comprise approximately 10% of all sinonasal malignancies and are found most frequently in the maxillary sinus and nasal cavity, at 36.9% and 34.0%, respectively. These malignancies may have similar clinical presentations to other tumors of this region and typically cause symptoms via mass effect. However, sinonasal mature B-cell NHL may also have symptoms that are more specific to B-cell lymphomas, namely fever and weight loss. These malignancies have a reported 5-year disease-specific survival of 63.5% to 68.0%, which compares favorably with survival rates of other sinonasal malignancies. Surgery serves virtually no role in the management of non-Hodgkin lymphoma, and these malignancies are primarily treated with a combination of chemotherapy and radiation therapy.