Sinus carcinoma

Sinus carcinoma is a malignant epithelial neoplasm arising from the mucosal lining of the paranasal sinuses, most commonly the maxillary sinus.[1][2] Squamous cell carcinoma (SCC) is the dominant histologic subtype, accounting for the majority of cases, followed by adenocarcinoma, adenoid cystic carcinoma, and several rarer entities.[3][4] These tumors are locally aggressive, with a propensity for insidious growth within the air-filled sinuses and eventual invasion of adjacent structures including the orbit, skull base, palate, and alveolar process.[2][4] Established risk factors include occupational exposure to wood dust, leather dust, nickel, and industrial fumes, as well as tobacco use and high-risk human papillomavirus (HPV) infection.[1][5] The air-filled sinus cavities permit asymptomatic growth, and most patients present with locally advanced disease.[2] Treatment is multimodality, centered on surgical resection with adjuvant radiation therapy.[1][6]

The 5th edition of the WHO Classification of Head and Neck Tumours (2022) classifies malignant epithelial neoplasms of the sinonasal tract into multiple categories, with squamous cell carcinoma subdivided into keratinizing and nonkeratinizing types.[7] The nonkeratinizing variant was previously termed "transitional" or "cylindrical cell" carcinoma.[8][9] Newly recognized entities in the 2022 classification include SWI/SNF complex-deficient sinonasal carcinoma and HPV-related multiphenotypic sinonasal carcinoma (HMSC).[7] Emerging molecularly defined entities include IDH2-mutant sinonasal undifferentiated carcinoma and DEK-AFF2 fusion-associated carcinoma.[3][10] NUT carcinoma, characterized by the NUT gene rearrangement, is now a distinct entity.[3][11] The term "sinus carcinoma" is a general clinical designation; precise histopathologic and molecular subtyping is essential for treatment planning.[1][6]

• Paranasal sinus and nasal cavity cancers account for less than 3% of all head and neck malignancies and approximately 0.5% to 1% of all cancers.[3][4]
• Estimated incidence is approximately 0.6 per 100,000 per year, with a male-to-female ratio of approximately 1.8–2:1.[3][5]
• Peak incidence occurs in the fifth and sixth decades of life.[1]
• The maxillary sinus is the most common paranasal sinus subsite, followed by the ethmoid sinus; frontal and sphenoid sinus carcinomas are rare.[1][2]
• SCC predominates, representing over half of all sinonasal malignancies; adenocarcinoma, adenoid cystic carcinoma, esthesioneuroblastoma, mucosal melanoma, and undifferentiated carcinomas constitute the remainder.[3][12]
• Adenocarcinoma has a strong association with wood and leather dust exposure and arises most commonly in the ethmoid sinuses.[1][4]

Sinus carcinomas are characteristically insidious, growing within air-filled spaces with few symptoms until locally advanced.[2]

Presenting symptoms

• Common: unilateral nasal obstruction, epistaxis, nasal discharge, and facial pain or pressure.[2][5]
• Occasional: facial swelling, hypoesthesia of the midface (V2 distribution), and epiphora.[2][5]
• Signs of advanced disease: proptosis, diplopia, and orbital pain from orbital invasion; toothache, dental mobility, widened periodontal ligament space, unhealed extraction socket, a mass in the upper alveolar ridge, or oroantral fistula from inferior extension through the sinus floor.[2][13]

Examination findings

• Visible mass on nasal endoscopy or intraoral examination in advanced cases.[2][14]
• Cranial nerve deficits, particularly V2 numbness, suggest perineural spread or skull base involvement.[2][14]
• Cervical lymphadenopathy is uncommon at presentation; nodal metastasis occurs in approximately 12% of maxillary sinus carcinomas.[1]

Red flags for the dental practitioner

Unexplained dental mobility, pain, or swelling in the posterior maxilla—particularly when unilateral and progressive—should raise suspicion for an underlying sinus malignancy.[13] A history of a nonhealing extraction socket or spontaneous oroantral communication warrants further investigation.[2][13]

Sinus carcinoma is most commonly encountered on dental radiographs as an incidental or secondary finding when the tumor extends inferiorly to involve the maxillary alveolar process or sinus floor. Panoramic radiography has limited sensitivity for sinus pathology, and three-dimensional imaging is necessary for definitive evaluation.[15][16]

Location and distribution

• The maxillary sinus is the most frequent paranasal sinus site; the posterior and lateral walls are commonly involved.[1][2]
• Inferior extension to the alveolar process and hard palate is characteristic of advanced maxillary sinus carcinoma.[6][17]
• Ethmoid sinus carcinomas may extend into the maxillary sinus, orbit, or anterior cranial fossa.[4][6]

Periphery and shape

• Margins are typically ill-defined and irregular, reflecting the infiltrative growth pattern of malignancy.[18][19]
• Unlike benign sinonasal masses that produce smooth bony remodeling, carcinomas characteristically demonstrate ragged, destructive margins.[20]

Internal architecture

• On panoramic radiography, the lesion appears as a poorly defined radiolucency or opacification of the maxillary sinus, often with loss of the normal sinus outline.[15][21]
• Complete opacification of the sinus is common in advanced disease but is nonspecific, as it may also be seen with retained secretions or inflammatory disease.[15][22]
• Calcification within the mass is uncommon in SCC; when present, it may suggest an alternative histology such as chondrosarcoma or represent residual destroyed bone fragments.[18]

Effects on teeth and adjacent structures

• Destruction of the sinus floor may produce widening of the periodontal ligament space, loss of the lamina dura, and external root resorption of the maxillary posterior teeth.[13]
• Dental mobility without an obvious odontogenic cause is a characteristic clinical-radiographic finding.[13]
• Tumor may spread from the sinus to the oral cavity through foramina in the sinus floor, through the marrow cavity of the alveolar process, or along branches of the superior alveolar neurovascular bundles.[17]

Bone destruction and cortical involvement

• Aggressive osteolytic destruction is the hallmark imaging feature of sinus SCC, in contrast to the pressure remodeling seen with slow-growing benign tumors.[20][22][23]
• Erosion of the infratemporal (posterior) wall of the maxillary sinus is characteristic of malignancy and is not seen in chronic sinusitis.[22]
• Destruction of the orbital floor, medial orbital wall, or pterygoid plates indicates locally advanced disease (T3–T4).[6]
• Skull base erosion, including the cribriform plate, raises concern for intracranial extension.[6][14]
• On cross-sectional imaging obtained via CBCT, cortical destruction of the sinus walls, loss of the antral floor, and perforation of the buccal cortex can be identified, aiding in the assessment of bone invasion. CBCT has demonstrated high accuracy for detecting bone invasion in maxillary SCC when interpreted by experienced observers, though it is limited in soft-tissue assessment. The ACR Appropriateness Criteria note that CBCT is not useful in the workup of sinonasal masses because of its limitations in assessing soft-tissue structures.[20][24][25][26]

Growth pattern and extent

• Sinus carcinomas grow in an expansile-destructive pattern, enlarging the sinus while simultaneously destroying its walls.[22]
• Extension into the nasal cavity, contralateral sinus, pterygopalatine fossa, infratemporal fossa, or orbit may be evident on cross-sectional imaging.[2][6]
• Perineural spread along V2 through the infraorbital canal and foramen rotundum is characteristic of both SCC and adenoid cystic carcinoma; foraminal widening on thin-section imaging is a key finding.[4][14]

Medical CT

Contrast-enhanced CT of the neck is the primary imaging modality for detection, localization, and osseous staging of sinus carcinoma.[4][6] CT provides superior delineation of the sinonasal skeleton, allowing precise characterization of bony destruction versus remodeling, which helps distinguish aggressive malignancies from slow-growing benign masses.[4][20] Sinus SCC characteristically demonstrates osteolytic destruction with an enhancing soft-tissue mass and complete sinus opacification.[22][23] Thin-section CT with multiplanar reformats can detect skull base foraminal widening suggestive of perineural tumor spread.[4]

MRI

MRI is complementary to CT and is preferred for evaluating soft-tissue extent, orbital and intracranial invasion, perineural spread, and differentiation of tumor from obstructed sinus secretions.[6][14] On MRI, SCC typically demonstrates intermediate T1 signal, intermediate-to-high T2 signal (isointense to gray matter), and heterogeneous enhancement.[19][27] Retained secretions in obstructed sinuses show characteristic high T2 signal and lack of enhancement, allowing distinction from solid tumor.[6] Diffusion-weighted imaging may aid in differentiating SCC from lymphoma (lower ADC in lymphoma) and melanoma (lower ADC in melanoma).[19][28]

FDG-PET/CT

FDG-PET/CT may be considered for initial staging to evaluate for regional and distant metastatic disease and is useful for detecting occult primary sites.[6][29] Sinonasal SCC is characteristically FDG-avid.[29]

Sinus carcinoma must be distinguished from other aggressive sinonasal masses and from inflammatory conditions that can produce sinus opacification. The key diagnostic challenge is differentiating malignancy from chronic sinusitis or benign neoplasms when a unilateral opacified sinus with bone changes is encountered on dental imaging.

Biopsy is essential for definitive diagnosis, as imaging features overlap substantially among sinonasal malignancies.[20] The highest-risk diagnostic pitfall is misinterpreting an aggressive sinus carcinoma as chronic sinusitis, delaying diagnosis; any unilateral sinus opacification with bone destruction warrants urgent tissue sampling and cross-sectional imaging.[2][14]

Squamous cell carcinoma

SCC is subdivided into keratinizing and nonkeratinizing types.[9][32] Keratinizing SCC is the most common variant, composed of nests and sheets of malignant squamous epithelium with intercellular bridges and keratin pearl formation.[32][33] Nonkeratinizing (cylindrical cell) SCC features ribbons and stratified masses of cells with palisading perpendicular to the basement membrane and is strongly associated with high-risk HPV, particularly type 16.[9][32] Other recognized variants include papillary, basaloid, and spindle cell (sarcomatoid) SCC.[33]

Radiologic-pathologic correlation

The pattern of bone destruction correlates with histologic subtype: SCC characteristically produces aggressive osteolytic destruction, whereas adenoid cystic carcinoma tends to show a more gradual, cribriform pattern of bone erosion with perineural tracking.[23][31] Homogeneous masses with minimal bone destruction favor lymphoma over carcinoma.[28]

Molecular classification

The 2022 WHO classification emphasizes molecular subtyping of sinonasal carcinomas:[7]

• HPV-associated SCC: predominantly nonkeratinizing; strong p16 expression; HPV RNA ISH is the recommended confirmatory test. HPV-associated tumors favor the nasal cavity and ethmoid sinus and carry a more favorable prognosis.[9][34][35]
• SWI/SNF complex-deficient carcinomas: loss of SMARCB1 (INI-1) or SMARCA4 (BRG1); associated with aggressive behavior and poor disease-free survival.[3][11]
• NUT carcinoma: defined by NUT gene rearrangement; presents in younger patients with an inferior prognosis.[3][11]
• IDH2-mutant carcinoma: an emerging entity currently classified under sinonasal undifferentiated carcinoma.[7][10]

Accurate histopathologic and molecular classification is paramount, as it directly influences treatment decisions and prognostic counseling.[1][6]

Workup and referral

The NCCN Guidelines for Head and Neck Cancers recommend complete head and neck CT with contrast and/or MRI with and without contrast for initial evaluation of maxillary and ethmoid sinus tumors.[6] Biopsy is performed preferably via a transnasal route; canine fossa puncture and Caldwell-Luc approaches should be avoided.[6] Dental and prosthodontic evaluation is recommended as part of the multidisciplinary workup.[6] Referral to a center with expertise in sinonasal malignancies is advised given the rarity and histopathologic diversity of these tumors.[1][6]

Staging

The AJCC 8th edition TNM system stages maxillary sinus carcinomas from T1 (tumor limited to mucosa without bone erosion) through T4b (invasion of orbital apex, dura, brain, middle cranial fossa, or clivus).[6] Nasal cavity and ethmoid sinus tumors are staged separately.[6]

Treatment

• T1–T2, N0 disease: surgical resection is the primary treatment. Observation is appropriate with negative margins for non-adenoid cystic histologies. Positive margins warrant re-resection if feasible, followed by radiation therapy.[1][6]
• T3–T4a, N0 and N+ disease: complete surgical resection (maxillectomy) with neck dissection for node-positive disease, followed by adjuvant radiation therapy or chemoradiation based on pathologic features. Adverse features (positive margins, close margins, extranodal extension) prompt consideration of concurrent systemic therapy with radiation.[1][6]
• T4b disease: definitive radiation therapy or chemoradiation; enrollment in clinical trials is encouraged.[1]
• Radiation therapy: IMRT or proton therapy is recommended to minimize dose to critical structures including the orbits, optic nerves, and frontal lobes. Definitive doses range from 66 to 70 Gy; postoperative doses are 60 to 66 Gy for high-risk areas.[6]
• Systemic therapy: high-dose cisplatin is the preferred concurrent agent; carboplatin/fluorouracil is an alternative. For neuroendocrine histologies (SNUC, SNEC, small cell), platinum/etoposide-based regimens are used.[6]

Prognosis

• Overall 5-year survival for all sinonasal malignancies is approximately 40%, varying substantially by histology and stage.[1]
• Local recurrence is the most common mode of treatment failure for maxillary sinus carcinoma.[1]
• HPV-positive sinonasal SCC carries a more favorable prognosis than HPV-negative disease.[33][35]
• Negative surgical margins are a critical prognostic factor; margin status significantly influences progression-free survival.[1][36]
• Undifferentiated carcinomas (SNUC, small cell, SNEC) and NUT carcinoma carry the poorest prognosis.[1][11]

HPV and molecular testing

The College of American Pathologists recommends HPV testing for all sinonasal SCC specimens, regardless of histologic subtype.[34] RNA in situ hybridization for high-risk HPV is the preferred testing method; p16 immunohistochemistry alone is insufficient due to a higher false-positive rate in sinonasal SCC compared with oropharyngeal SCC.[34] HPV-associated sinonasal SCC has a propensity for the nasal cavity and ethmoid sinus, whereas HPV-independent SCC favors the maxillary sinus.[35]

Schneiderian papilloma and malignant transformation

Inverted papilloma (Schneiderian papilloma, inverted type) is a recognized precursor lesion for sinonasal SCC.[4][30] SCC arising within inverted papilloma demonstrates more extensive bone destruction than the parent lesion and requires aggressive surgical management.[30]

Dental implications of treatment

Patients undergoing radiation therapy to the maxillary region require comprehensive pre-radiation dental evaluation to identify teeth at risk for osteoradionecrosis and to perform necessary extractions before treatment.[6] Prosthodontic rehabilitation with an obturator is commonly required after maxillectomy; zygomatic implants or microvascular free-flap reconstruction may be considered for large defects.[1]