Clinical Features

Slow growth eventually produces unilateral nasal obstruction, occasionally epistaxis, or serosanguinous discharge, or produces a mass on the palate affecting denture fitting, but the lesions can achieve spectacular proportions if neglected (Fig. 7.1). In the series of Compagno and Wong6 the patient age range for sinonasal pleomorphic adenomas was 3 to 82 years, mean 42 years, with only a slight female preponderance in contrast to the situation in the major salivary glands where it is most frequent in women. In the 56 reported cases, the ages ranged from 5 to 67 years (mean 42.3 years) and the male-to-female ratio was 1.2:1. Fifty-two percent arose on the septum and 31% on the lateral wall (usually the inferior turbinate); one case affected the rostrum of the sphenoid, one the columella, and two the nasopharynx.

Imaging

The features are those of any benign unilateral solid mass and are not specific (Fig. 7.2).14 There can be some local excavation of adjacent bone on CT, but there is little if any active destruction.35,37 Calcified foci and irregular enhancement has been described on CT with contrast.17

The tumor may be multilobulated and better defined on MRI. Fat-suppressed contrast-enhanced T1-weighted (T1W) spin-echo images showed marked curvilinear enhancement with small unenhanced foci.17 In the 9 patients reported by Wu et al40 there was low intensity on T1W images but intermediate to high on T2W sequences.

Histological Features and Differential Diagnosis

Monomorphic adenomas can be divided into myoepithelial, basaloid, trabecular/tubular, or oncocytic.

The diagnosis of pleomorphic adenoma requires the demonstration of epithelial (glandular) and mesenchymal (or myoepithelial) components. It is usually a lobulated and circumscribed lesion composed of epithelial tissue mixed with mucoid, myxoid or chondroid material, but a true capsule is rarely present.15 Intranasal pleomorphic adenomas have a similar immunohistochemical profile to their counterparts in the major salivary glands that depends on the dominant phenotype of the tumor. Most of the epithelial components will express various cytokeratins, whereas the myoepithelial component will express smooth muscle actin, S100, GFAP, CD10, and p63.19,41–43 Very occasionally the myoepithelial component is such that the tumor is designated as a myoepithelioma, which carries a separate ICD code in the WHO classification (ICD-O 8982/0). This is an exceptionally rare tumor in the sinonasal region and is more often encountered in the parotid and palate. It may be regarded as part of the spectrum of pleomorphic adenomas, being benign but more likely to recur.

The most important differentiation for pleomorphic adenoma is from malignant glandular tumors such as adenoid cystic type, adenocarcinoma, and the occasional carcinoma ex pleomorphic or true malignant mixed tumor.

Carcinoma Ex Pleomorphic Adenoma and Malignant Mixed Tumors

These extremely rare malignant variants can arise either within an existing pleomorphic adenoma or de novo. Only a handful of cases (<20) have been reported, mainly arising on the palate or septum.44–57 Although factors relating to the prognosis of these tumors elsewhere have been discussed46,54 it is not known whether they can be extrapolated to this site.

Clinical Features

Sinonasal oncocytomas occur equally in men and women, the reported age range being 12 to 84 years (mean 64 years), whereas elsewhere in the body they are more common in the elderly and in women.25 Two of our three patients were female. Patients present with nasal obstruction, nasal discharge, and epistaxis. More extensive and malignant lesions will produce tissue destruction with a visible swelling due to the mass breaking into the orbit or cheek together with associated epiphora, diplopia, proptosis, edema, and paresthesia.

Imaging

There are nonspecific features of a soft tissue mass with additional obstruction of adjacent sinuses and bone destruction depending on the aggressiveness of the lesion.

Histological Features and Differential Diagnosis

Oncocytomas are, as one might expect, composed of oncocytes which are large cuboidal or columnar cells with an abundant eosinophilic cytoplasm. This cytoplasm is particularly rich in mitochondria, which give it a granular appearance, and was first confirmed by electron microscopy.26 Lymphocytes are very rare within the tumor, which is positive for cytokeratin and epithelial membrane antigen but negative for S100. This must be distinguished from oncocytic metaplasia, which is not uncommon in the upper respiratory tract, oncocytic papillomas, and malignant oncocytomas, which are extremely rare. Oncocytic metaplasia may occur due to trauma or be a degenerative process. The other differential diagnoses include adenocarcinoma and adenoid cystic carcinoma.

There is no true capsule but compression of adjacent tissue may produce a “pseudo-capsule.”

In the major salivary glands, the benign forms are described as being papillary or cystic, whereas the more malignant appear solid.