Oncocytic sinonasal papillomas (OSP) or cylindrical cell papillomas are a rare form of Schneiderian papillomas and benign epithelial sinonasal tumours arising from the Schneiderian epithelium of the nasal cavity and paranasal sinuses.
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Epidemiology
Oncocytic sinonasal papillomas are the least frequent type of sinonasal papillomas 1,2. Similar to inverted papillomas they are seen in a wide age range with a peak in the fifth and sixth decade 1. They have no gender predilection 1.
Diagnosis
The diagnosis of oncocytic sinonasal papillomas is made by their location, endoscopic appearance and histological features 3.
Clinical presentation
Clinical symptoms are similar to the other variants and include nasal obstruction, rhinorrhoea, epistaxis and the presence of a mass lesion 1,3. They might be also found incidentally on imaging studies.
Complications
Oncocytic sinonasal papillomas might undergo a malignant transformation in up to one-sixth of cases 1,4.
Pathology
Location
Oncocytic sinonasal papillomas typically grow at the lateral nasal wall and paranasal sinuses 2.
Subtypes
Subtypes include cylindrical cell papilloma and columnar cell papilloma.
Macroscopic appearance
Macroscopically oncocytic sinonasal papillomas have been described as reddish polyps sometimes featuring a cerebriform appearance and a firm consistency 1.
Microscopic appearance
Histologically primary oncocytic sinonasal papillomas are characterised by the following 1-3:
- pseudostratified cuboid to columnar cells with well defined cellular borders
- prominent granular eosinophilic cytoplasm
- small hyperchromatic nuclei
- exophytic and inverted growth patterns
- some keratinisation
- prominent intraepithelial microcysts and neutrophilic microabscesses
Genetics
Oncocytic sinonasal papillomas are associated with KRAS mutations 1. They are typically negative for EGFR mutations 2.
Radiographic features
Oncocytic sinonasal papillomas are characterised by a rather nonspecific septate or striated appearance and a lobulated shape 1,5.
CT
On CT they appear isodense and do not have any calcifications. They often cause thinning of the adjacent bone 5.
MRI
Like inverted papilloma, oncocytic papillomas might show a cerebriform pattern or striations on T2 weighted and enhanced images 3,5. In addition, oncocytic sinonasal papillomas are more likely to show 5:
- heterogeneous high-signal on T1 weighted images
- intralesional cystic changes
Signal characteristics
- T1: heterogeneous iso to hyperintense
- T2: iso to hyperintense
- DWI: iso to hypointense
- T1 C+(Gd): homogeneous enhancement (less than surrounding mucosa)
Radiology report
The radiological report should include a description of the following features:
- location, shape and size of the lesion
- associated focal hyperostosis
- intralesional cystic changes and heterogeneous high T1 signal
Treatment and prognosis
Management includes resection with clear margins. Long term prognosis is excellent if resection is complete and in the absence of malignant transformation 1. Recurrences are common with incomplete removal and usually develop within 5 years of the initial presentation 3,4.
History and etymology
The American pathologist VJ Hyams introduced the first histological classification of sinonasal papillomas in 1971 which included cylindrical cell papillomas that are now known as oncocytic papillomas 1,7.
Differential diagnosis
The differential diagnosis of exophytic sinonasal papillomas include the following 3:
- inverted papillomas
- exophytic sinonasal papillomas
- low-grade papillary adenocarcinoma
- rhinosporidiosis
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