Non-Neoplastic Lesions of the Nasal Cavity, Paranasal Sinuses, and Nasopharynx

Clinical Features

Rhinosinusitis is a common condition that can be caused by myriad etiologies, including allergies (most common), infections, aspirin intolerance, exposures to toxins or medications, pregnancy, systemic diseases, among others. Rhinosinusitis can also be idiopathic, with no known cause. Regardless of etiology, patients share the symptoms of nasal obstruction and discharge.

Acute rhinosinusitis is typically infectious, either viral (e.g., rhinovirus, adenovirus, respiratory syncytial virus, among others) or bacterial ( Streptococcus pneumoniae , Haemophilus influenzae , among others). Viral rhinosinusitis results in a watery nasal discharge, whereas bacterial disease results in a mucopurulent discharge, headache, and fever. Bacterial rhinosinusitis can occasionally be superimposed on viral disease.

Chronic rhinosinusitis (i.e., symptoms lasting longer than 12 weeks) is most often allergic in etiology as a result of an IgE-mediated reaction. Patients with allergic rhinosinusitis complain of a clear nasal discharge, sneezing, and itching after exposure to the offending allergen. Clinical examination reveals sinonasal mucosa that is edematous, pale, and sometimes bluish in color. Inflammatory polyps, as described later, are often seen in this setting.

By imaging, inflamed sinuses demonstrate opacification and mucosal thickening ( Fig. 1.1A ). Air-fluid levels are classically identified in acute disease (see Fig. 1.1B ).

Pathologic Features

Microscopic Findings

Rhinosinusitis exhibits sinonasal mucosa with a submucosal inflammatory infiltrate. The inflammatory cells are generally composed of lymphocytes, plasma cells, macrophages, and eosinophils, which predominate in allergic disease ( Fig. 1.2 ). Acute rhinosinusitis is characterized by increased neutrophils, especially when associated with a bacterial etiology. There is often a component of stromal edema, which leads to the development of inflammatory polyps (described in detail in the next topic). The surface epithelium may also demonstrate changes, including inflammation, squamous metaplasia ( Fig. 1.3A ), or reactive papillary hyperplasia (so-called papillary sinusitis ) (see Fig. 1.3B ).

Differential Diagnosis

The diagnosis of rhinosinusitis is usually not difficult. Many of the changes overlap with sinonasal inflammatory polyps, and the distinction between the two entities is not important. In cases with squamous metaplasia and/or reactive papillary hyperplasia of the surface epithelium, sinonasal papilloma can enter the differential diagnosis. Sinonasal papillomas have squamous or squamoid epithelium that is also thickened, proliferative with endophytic and/or exophytic growth, and infiltrated by neutrophils with microabscesses. Rarely, adenocarcinoma may enter the differential diagnosis when there is a reactive proliferation of seromucinous glands.

Prognosis and Therapy

Acute viral rhinosinusitis is treated symptomatically, whereas bacterial disease requires antimicrobials. Chronic allergic sinusitis is treated with antihistamines, intranasal corticosteroids, and/or allergic desensitization. Patients with chronic rhinosinusitis refractory to medical therapy may require endoscopic surgery. Rhinosinusitis is generally not life-threatening, with the rare exception of untreated bacterial infection that can lead to infection of the orbit or meninges.

Clinical Features

Inflammatory polyps are associated with many conditions. They are most often seen in the setting of allergic rhinosinusitis but may also be seen in the setting of infections, asthma, aspirin intolerance, cystic fibrosis, diabetes mellitus, and other conditions. Inflammatory polyps are typically seen in adults (except for cystic fibrosis-associated polyps), with no sex predilection. They involve the nasal cavity (especially the lateral wall) and maxillary and ethmoid sinuses and are usually bilateral ( Fig. 1.4A ). In addition to the symptoms of the underlying condition (e.g., allergies), sinonasal inflammatory polyps may cause nasal obstruction and pain. A subtype of inflammatory polyp known as antrochoanal polyp arises from the maxillary antrum and extends through the sinus ostia into the nasal cavity, nasopharynx, or oral cavity (see Fig. 1.4B ). Antrochoanal polyps are usually seen in younger patients (teenagers and young adults), usually males, and are typically unilateral.

Pathologic Features

Microscopic Findings

The most prominent feature of a sinonasal inflammatory polyp is submucosal edema beneath an intact respiratory epithelium ( Fig. 1.5A ). The subepithelial basement membrane is typically hyalinized (see Fig. 1.5B ). There is usually a mild to moderate infiltrate of chronic inflammatory cells with a predominance of eosinophils (see Fig. 1.5B ). Scattered stellate or spindled fibroblasts are seen, some of which may exhibit enlarged, hyperchromatic nuclei (see Fig. 1.5C ). Larger inflammatory polyps may demonstrate prominent submucosal hemorrhage with fibrin deposition or infarction, a pattern that has been referred to as “angiomatous” or “angiectatic” (see Fig. 1.5D ).

Antrochoanal polyps have a similar appearance but tend to be more fibrotic and less edematous ( Fig. 1.6A ), have fewer eosinophils, and lack a hyalinized basement membrane (see Fig. 1.6B ). Bizarre stromal cells are more common in antrochoanal polyps than in inflammatory polyps.

Differential Diagnosis

The diagnosis of sinonasal inflammatory polyp is usually straightforward. When there is prominent fibrin deposition, amyloidosis is a consideration. True amyloid is positive with Congo red showing apple-green birefringence, in contrast to fibrin. In angiomatous polyps in which recanalizing vessels are prominent, a vascular or lymphatic neoplasm could be considered. Recognizing the context of the vessels (i.e., with organizing fibrin within a sinonasal polyp) is useful in avoiding this pitfall. The fibrous stroma and occasional nasopharyngeal location of antrochoanal polyps are somewhat reminiscent of nasopharyngeal angiofibroma. In addition, both tumors, typically as unilateral masses, arise in younger men. Recognizing the dilated, “staghorn” appearance of the vessels is important for diagnosing angiofibroma; the vessels of antrochoanal polyp are typically small and inconspicuous. In difficult cases, immunohistochemistry for beta-catenin and androgen receptor may be used: the stromal cells of angiofibroma are positive for both, whereas antrochoanal polyps are negative. The atypical stromal cells of sinonasal inflammatory polyps can, in some cases, be alarming and raise the possibility of a sarcoma such as embryonal rhabdomyosarcoma. However, the atypical stromal cells of benign polyps are singly and randomly distributed, do not aggregate (e.g., no “cambium” layer characteristic of embryonal rhabdomyosarcoma), are not mitotically active, and are negative for desmin and myogenin. Respiratory epithelial adenomatoid hamartoma (REAH) tends to show widely spaced glands, surrounded by a thick, eosinophilic basement membrane, showing connections of the invaginations to the surface. Finally, one must be sure to exclude the presence of another sinonasal neoplasm such as sinonasal papilloma that are often seen in association with inflammatory polyps.

Prognosis and Therapy

These are benign lesions. Treatment includes endoscopic surgery in addition to treatment of the underlying medical cause (e.g., nasal steroids for allergic polyps).

Clinical Features

Sinus mucoceles can occur in any age or sex. They result from any disease that obstructs the sinus outflow tract (ostium or duct), most commonly chronic sinusitis, but also occasionally trauma, neoplasms, or other causes. The obstruction leads to expansion of the involved sinus, usually frontal or ethmoid ( Fig. 1.7A ). Mucoceles can produce alarming clinical and radiographic features, including facial deformity, headaches, visual disturbances, proptosis, bone erosion and sclerosis, and rarely, invasion of the orbit or cranial cavity (see Fig. 1.7B ). Given these dramatic symptoms and radiographic features, a neoplastic process is often suspected clinically.

Pathologic Features

Microscopic Findings

The microscopic features of mucoceles are typically underwhelming (particularly in the setting that is suspicious for malignancy) and closely mimic normal sinonasal tissue. The sinonasal tissue sometimes has an attenuated appearance resembling a cyst lining ( Fig. 1.8A and B ). Epithelial squamous metaplasia, fibrosis, a rim of reactive bone, or cholesterol granuloma formation can also be seen. Because of their nonspecific nature, a definitive diagnosis cannot be made on histologic grounds without clinical or radiographic input.

Differential Diagnosis

The main diagnostic consideration is normal sinonasal tissue. Clinical and radiographic correlation is needed to make the distinction. Sinonasal polyps or a salivary gland mucocele may also be in the differential. An unsampled neoplasm may be the cause of the obstruction leading to a mucocele.

Prognosis and Therapy

Sinus mucoceles are treated by surgical excision. The underlying cause of the obstruction (e.g., chronic sinusitis) should also be addressed. The prognosis is excellent.

Clinical Features

AFS most often affects children and young adults, with no sex predilection. Affected patients present with nasal discharge along with allergic-type symptoms such as nasal stuffiness, facial pressure, and fullness. Patients are often observed to have firm, viscous, foul-smelling mucin within their affected sinuses. In addition, patients typically exhibit peripheral eosinophilia and elevated serum IgE levels. In severe cases, patients uncommonly may exhibit facial asymmetry with bone destruction.

Pathologic Features