Sinonasal adenocarcinoma

Sinonasal adenocarcinomas are primary tumors of the sinonasal region with glandular differentiation. They are grossly classified as salivary and non-salivary subtypes. However, generally in the literature and IARC/WHO classification, the term "sinonasal adenocarcinoma" refers to non-salivary adenocarcinomas unless otherwise specified ¹. This article refers specifically to non-salivary adenocarcinomas.

They can be classified based on the glandular components as intestinal or non-intestinal subtypes, which have their respective risk factors, clinical presentation, imaging characteristics, and prognosis.

Epidemiology

Sinonasal adenocarcinomas are the third most common sinonasal malignancy, accounting for 5-10% of all sinonasal malignancies. Males are most affected (75-90%) between 55-60 years of age ^2,3.

Intestinal type adenocarcinomas are strongly associated with wood dust exposure, with wood-workers having a 900-1000x increased risk in comparison to the normal population. These exposure-related sinonasal adenocarcinomas tend to appear in the ethmoidal sinuses and nasal cavity (which has a higher presence of inhaled promoters), whilst non-exposure-related adenocarcinomas arise more frequently in the maxillary sinus, similar to other non-glandular sinonasal carcinomas ^2,3.

Clinical presentation

Clinical presentation depends greatly on the central tumoral focus and on its invasive components. Generally, those arising in the nasal cavity and ethmoid region present in earlier stages with complaints of nasal congestion and obstruction mimicking sinusitis.

Tumors arising in the sinuses however present at later stages, often with signs of invasion and compression of nearby structures, such as facial pain, proptosis and diplopia, headache or neurological symptoms.⁴

Pathology

Sinonasal adenocarcinomas are glandular neoplasms. They are classified into intestinal type and non-intestinal type. This is due to the specific histological and immunohistochemical features of intestinal type sinonasal adenocarcinomas, along with the marked association with wood-dust exposure ⁵.

Intestinal type sinonasal adenocarcinomas are morphologically very similar to adenocarcinoma or adenoma of the small intestine, or even to normal intestinal mucosa. It can be classified as different histological subtypes (papillary, colonic, solid, mucinous, mixed), and each of these subtypes has a different prognosis ⁵.

Non-intestinal type sinonasal adenocarcinomas are a more heterogeneous group, not associated with wood-dust exposure. They can be grossly classified as high- or low-grade. Low-grade non-intestinal sinonasal adenocarcinomas are circumscribed or invasive, and consist of multiple small glands or acini, with scarce associated solid-stroma. High-grade non-intestinal sinonasal adenocarcinomas are composed mainly of a solid stromal component with a lesser proportion of glandular structures. They have marked pleomorphism and mitotic activity ⁵.  

Radiographic features

Salient general imaging features are those of a badly defined, heterogeneously enhancing mass in the sinonasal or skull base region. They may appear anywhere in the sinonasal cavities, however, intestinal-type and low-grade non-intestinal type sinonasal adenocarcinomas have a higher tendency to affect ethmoid and nasal cavity, whilst high-grade non-intestinal type sinonasal adenocarcinomas more frequently affect maxillary sinuses. 

CT

CT is the best method for evaluating the bone involvement associated with the mass. It tends to have an aggressive pattern of bone destruction, with bone destruction and invasion of nearby structures. Diffuse heterogeneous contrast enhancement can also be seen.

MRI

MRI signal is intermediate on T1 and T2, with possible high-T1 hemorrhagic foci.

Treatment and prognosis

These tumors are generally locally invasive, with a high tendency to recur. In a general sense management includes:

• complete surgical resection is indicated in early disease (stages I and II) 
• postoperative radiotherapy should be performed if there are risk factors for recurrence (positive or uncertain margins, risk histological subtypes, perineural invasion)
• Initial surgical resection with adjuvant radiotherapy is the preferred modality for locally advanced disease (stages III and IV), 
• Radiotherapy or combined chemoradiotherapy may be an alternative for definitive surgery in non-surgical candidates,

The degree of orbital and/or intracranial involvement, however, can have important surgical implications and should be clearly detailed in the radiological report ⁶.

Differential diagnosis

General imaging differential considerations include:

• sinonasal squamous cell carcinoma (or sinonasal carcinoma): often similar in appearance (usually less heterogeneous) should always be considered in sinonasal malignancy
• sinonasal adenoid cystic carcinoma: mostly affects maxillary sinus and nasal cavity; very high propensity for perineural tumor spread ³
• sinonasal undifferentiated carcinoma (SNUC): mostly affects ethmoid and nasal cavity; early nodal metastases ³
• sinonasal lymphoma: mainly affects paranasal sinuses and simulates benignity, with frequent bone remodeling more than destruction; homogeneous contrast-enhancement with homogeneous diffusion restriction, with scarce or no necrosis, are characteristic ³
• sinonasal melanoma: mainly affects the inferior nasal fossa; lesions are characteristically hypervascular and hemorrhagic; can sometimes simulate benignancy, with frequent bone remodeling instead of destruction; if the tumor is the melanotic subtype, they can have a characteristic intrinsic T1 hyperintensity ³
• esthesioneuroblastoma: centered on the cribriform plate, with characteristic dumbbell shape affecting ethmoid sinuses inferiorly and invading anterior cranial fossa superiorly; often show adjacent bone hyperostosis, bone remodeling and nasal cavity expansion; intracranial tumor-margins often show characteristic peripheral T2-hyperintense cysts ³