Sinonasal tumors are rare, diverse, complex lesions with overlapping demographic and clinical features. Malignant tumors are more common, with a grave prognosis, and require biopsy for accurate diagnosis. This article briefly reviews the classification of sinonasal tumors and provides imaging examples and imaging characteristics of each clinically important nasal and paranasal mass lesions. Although there are no true pathognomonic imaging features, it is important for the radiologist to have a broad knowledge of the various CT and MR imaging findings that can help narrow the differential diagnosis and aid in early diagnosis and mapping of tumor for treatment planning.
Key points
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It is vital for surgeons and radiologists to be familiar with imaging findings that raise suspicion of a sinonasal tumor given the nonspecific clinical presentation that mimics inflammatory rhinosinusitis.
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Although there is considerable overlap in the imaging findings of sinonasal tumors, certain diagnostic features on computed tomography (CT) and MRI can help narrow the differential and assist in preoperative diagnosis.
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CT is better in the assessment of the osseous matrix and cortical bone involvement of the skull base.
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MRI is superior for evaluation of the tissue components of the tumor, bone marrow involvement, and extension along skull base foramen and intracranial extension.
Introduction
The sinonasal tract can be involved by a variety of neoplasms. The authors have adopted a simplified classification of sinonasal neoplasms that divides sinonasal tumors based on benignity versus malignancy and tissue of origin in accordance with the World Health Organization classification scheme ( Table 1 ).
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Clinical presentation
The diagnosis of sinonasal tumors is often delayed because of nonspecific and subtle symptoms that can be similar to rhinosinusitis, such as purulent nasal discharge, epistaxis, nasal obstruction, headache, and facial pain. Clinical suspicion is the most important factor in the accurate diagnosis of sinonasal malignancy.
The relative age of the patient (>50 years) and the insidious onset of unilateral symptoms or recurrent epistaxis should alert the possibility of neoplasm as a cause of the patient’s symptoms. Approximately 40% are discovered at a locally advanced stage with presenting symptoms that include anosmia, epiphora, facial pain and swelling, visual disturbances, exophthalmos, diplopia, trismus, loose teeth, and cranial neuropathy. Shooting neuropathic pain along the distribution of the trigeminal nerve is typical of perineural spread. Orbital involvement at presentation is typically associated with worse prognosis. ,
Imaging
Computed tomography (CT) and magnetic resonance imaging (MRI) are complementary in the assessment of tumor size, morphology, invasion, and disease extent. CT is superior for evaluation of anatomic details, presence and type of calcifications and matrix of the tumor, and pattern of bone invasion, provides a bony map for surgery, and may help define the origin of the tumor.
MRI provides better contrast resolution and characterization of the soft tissue components of sinonasal tumors, evaluation of multicompartmental extension, detection of bone marrow infiltration, perineural spread, and intracranial extension. CT angiography or magnetic resonance angiography can be used to determine the relationship of the tumor to the intracranial course of the internal carotid artery and its branches and feeding vessels for hypervascular tumor.
PET/CT is a useful tool in the detection of nodal disease and distant metastatic spread in the setting of aggressive malignancies, evaluation of response to therapy, and detection of residual or recurrent tumor. More recently, 68-Ga DOTATATE PET/CT plays an important role in the evaluation and management of the rare somatostatin receptor expression sinonasal neuroendocrine tumors.
Benign neoplasms
Sinonasal Papilloma
Sinonasal papillomas are benign sinonasal tumors also known as Schneiderian papillomas, as they arise from the Schneiderian epithelium of the nasal cavity and the paranasal sinuses. , These account for approximately 2.5% of all sinonasal tumors and are histologically subdivided into 3 subtypes: inverted, oncocytic, and exophytic types. Of these, inverted papilloma (IP) is the most frequent type, seen 2.5 to 3 times more frequently in men compared with women and commonly occurring in the fifth and sixth decades of life. The inverted and oncocytic types usually arise from the lateral wall of the nasal cavity, whereas the exophytic type arises from the lower anterior nasal septum. The inverted and oncocytic types have a high incidence of recurrence with up to a 15% risk of malignant transformation to squamous cell carcinoma (SCC). ,
It is difficult to differentiate the 3 subtypes from each other on imaging; however, IP, the most common type, has a characteristic imaging appearance, which suggests the histologic subtype. On CT, IP is seen as a lobulated soft tissue mass centered along the lateral nasal wall and middle meatus. A cone-shaped focus of hyperostosis is often seen and points to the origin of the lesion ( Fig. 1 A ). Identification of this hyperostotic stalk is helpful in localizing and determining the extent of tumor during surgery, complete resection of which is necessary to prevent local recurrences. Intralesional calcifications are frequently seen. On MRI, a “convoluted cerebriform pattern” (CCP), seen as alternating lines of high and low signal intensity on T2 and postcontrast T1-weighted images, resembling cerebral gyri has been described ( Fig. 1 B, C). A focal loss of this CCP, necrosis within the mass, bone destruction, or extrasinonasal extension, is suggestive of malignant transformation to SCC ( Fig. 1 D–F). ,
Respiratory Epithelial Adenomatoid Hamartoma
Respiratory epithelial adenomatoid hamartoma (REAH) is a benign, polypoidal mass of submucosal glandular proliferation, most commonly found in the anterior half of the olfactory cleft or the posterior nasal septum/posterior nasal cavity. The median age of presentation is the sixth decade, and the tumor is 7 times more commonly seen in men compared with women. It is usually seen as an isolated lesion; however, concomitant association with sinonasal polyposis has also been reported.
Very often incidentally found, the lesion is seen as a homogeneously enhancing, well-defined soft tissue mass centered in the olfactory cleft on CT or MRI. REAH is frequently bilateral (40%) and causes widening of the clefts ( Fig. 2 ). Involvement of the anterior half of the olfactory cleft with significant widening is useful in differentiating this lesion from sinonasal polyposis. Absence of bone destruction helps differentiate this lesion from olfactory neuroblastoma, which occurs in a similar location.
Bening soft tissue tumors
Benign soft tissue tumors of the sinonasal cavities are rare and include nerve-sheath tumors, hemangioma, angiofibroma, myxoma, leiomyoma, and meningioma.
Hemangioma
Hemangioma is a benign vascular neoplasm occurring in the nasal cavity and is divided into 2 types, capillary and cavernous, based on the microscopic vessel size. Of the 2 types, capillary hemangiomas are more common, arising from the nasal septum, whereas the cavernous type arises from the lateral wall of the nasal cavity. Almost all intraosseous hemangiomas of the facial skeleton are of the cavernous type.
On CT, capillary hemangiomas are well-defined intensely enhancing masses with a hypodense peripheral rim ( Fig. 3 A ). On MRI, lesions demonstrate T1 hypointensity, T2 hyperintensity, and intense enhancement with a peripheral rim of nonenhancement ( Fig. 3 B, C). A washout pattern may be seen on dynamic contrast-enhanced study in approximately 75% of cases.
Because of their large size, cavernous intraosseous hemangiomas produce benign-appearing expansion and thinning of adjacent bone structures. CT is the most useful imaging technique for diagnosing an intraosseous cavernous hemangioma, showing a honeycomb appearance ( Fig. 3 D). Cavernous hemangiomas are predominantly hyperintense on T2-weighted images and heterogenous on all other sequences ( Fig. 3 E, F). Unlike capillary hemangiomas, cavernous hemangiomas demonstrate heterogenous enhancement on CT and MRI owing to bleeding and necrosis.
Nasopharyngeal Angiofibroma
Also known as juvenile nasopharyngeal angiofibroma (JNA), nasopharyngeal angiofibroma masses are almost exclusively found in adolescent and young men (mean age, 9–15 years) accounting for approximately 0.5% of head and neck tumors. , Clinical presentation is with obstructive symptoms and painless epistaxis. They are nonencapsulated, well-circumscribed, highly vascular polypoidal masses made of both vascular and fibrous stromal tissue. When they are large and extensive, symptoms may include proptosis, visual disturbances, and cranial nerve palsies. These tumors usually arise within the sphenopalatine foramen, close to the pterygopalatine fossa with extension into the posterior nasal cavity and nasopharynx.
On CT, a homogeneously and avidly enhancing well-defined soft tissue mass is seen in the posterolateral nasal cavity. Extension and widening of the pterygopalatine fossa with anterior bowing of the posterior wall of the maxillary sinus are typical ( Fig. 4 A). On MRI, a hypointense T1/heterogeneous T2 avidly enhancing hypervascular mass is seen ( Fig. 4 B, C). Flow voids may be seen within the mass secondary to hypervascularity. MRI is useful in delineation of the tumor extent, especially when large and extending into the orbit, paranasal sinuses, infratemporal fossa, nasopharynx and intracranially. Angiography is usually performed before surgery for identification and embolization of feeding arterial vasculature to reduce intraoperative blood loss. Arterial supply is most commonly from the internal maxillary and ascending pharyngeal branches of the external carotid artery. ,
Fibro-osseous lesions
The term “fibro-osseus” refers to a category of benign neoplasms or tumorlike lesions, with ossifying fibroma (OF), osteoma, and fibrous dysplasia being the most common. Osteomas are most common in the frontoethmoid region and appear as well-defined sclerotic lesions (compact bone) with possible trabeculae (cancellous bone) and lucent areas on CT ( Fig. 5 A ) and signal void on MR ( Fig. 5 B). Classic fibrous dysplasia typically has an expansile, ground glass appearance on CT with intact cortical bone ( Fig. 5 C), and the pagetoid and cystic variants may demonstrate mixed lucent and sclerotic areas. On MRI, lesions with a high fibrous content show a low to intermediate T1 signal intensity and T2 low signal in mineralized areas and high signal in cystic lesions ( Fig. 5 D). Active lesions markedly enhance.
Ossifying Fibroma
Ossifying fibroma is a rare, expansile benign tumor that arises predominantly from the maxilla or the mandible and is much more common in women aged 20 to 40 years. In rare instances, it may arise in the nasal cavity and paranasal sinuses. ,
On CT, in the early stages, OFs demonstrate a soft tissue density fibrous center surrounded by a thick bony cortex. In later stages, there is progressive filling of the center with mature bone ( Fig. 5 E). , On MRI, OF is low to intermediate signal on T1-weighted images, hypointense on T2-weighted imaging with the fibrous component demonstrating enhancement ( Fig. 5 F–H). OF has been reported to be associated with aneurysmal bone cysts, in which case, fluid-fluid levels can be seen (see Fig. 5 F).
Other tumors
Sinonasal Meningioma
Extracranial meningiomas represent approximately 1% to 2% of all meningiomas. These are seen more commonly as an extension from an intracranial site. Rarely, these can be seen as a primary tumor within the nasal cavity, paranasal sinuses, or the nasopharynx. , Tumor origin from arachnoid cells present in the nerve or vessel sheath at the exit foramina, or an origin from undifferentiated or multipotent mesenchymal cells have been proposed as possible mechanisms of development of tumor. Histologically, the tumors demonstrate features similar to intracranial meningiomas. Most are grade 1 tumors; however, a few grade 2 and 3 meningiomas have been reported. , These extracranial tumors are mostly seen in adults around the fifth decade of life, with a few cases described in children. , ,
CT demonstrates an isodense or hyperdense homogenously and intensely enhancing mass. Underlying calcification may be seen. Adjacent bone erosion or hyperostosis can be seen similar to intracranial meningiomas. MRI features are isointense to hypointense T1 signal, mixed predominantly isointense to hypointense T2 signal, restricted diffusion, and intense homogenous enhancement ( Fig. 6 A–C ). Although most of the extracranial meningiomas have similar imaging characteristics as the intracranial type, caution needs to be exerted when interpreting extracranial meningiomas based on signal characteristics on MRI, because different signal intensities between the intracranial and extracranial components can sometimes be present.
Diagnosis is usually straightforward in cases of direct sinonasal extension of intracranial meningioma. In cases of primary sinonasal lesions, typical imaging features of meningioma are helpful in making a diagnosis ( Fig. 6 D–F). However, given the rarity of these lesions, histopathology is often needed for diagnosis.
Sinonasal Ameloblastoma
Ameloblastomas are benign odontogenic tumors with aggressive features, which most commonly arise from the posterior mandible and less frequently (15%) from the maxilla. Rarely, the sinonasal cavity can be a primary site for these tumors. Primary sinonasal ameloblastomas are more frequent in men and present around the sixth decade, occurring later as compared with those in the jaw. ,
On CT, they appear as a solid soft tissue mass occupying the nasal cavity or the paranasal sinuses with bone remodeling or occasionally erosion ( Fig. 7 A). This imaging appearance is different from their counterpart in the jaw where they have a multicystic or “bubble-like” appearance. MRI findings are not pathognomonic, and lesions are usually isointense to muscle and enhance intensely ( Fig. 7 B, C). Primary sinonasal ameloblastoma requires a biopsy for confirmation.
