December 2012 - Dr. Stephanie Petkiewicz
Clinical history: 70 year old female with an intra-nasal polyp.
Schneiderian Papilloma, Inverted Type
Histogenesis: Arises from the respiratory mucosa of the sinonasal tract (Schneiderian membrane).
Gross Features: Soft, fleshy, tan. The stroma is often edematous.
¬Histologic Features: The invaginated mucosa is expanded by many cell layers of nonkeratinizing epithelium. At the surface of the epithelium ciliated cells may be present. Intermixed, within the nonkeratinizing epithelium are mucous cells with intracytoplasmic mucin globules and eccentric nuclei. Mitotic figures may be present, most commonly in the basal layers, but may be present higher up without concern of dysplasia; atypical mitoses, however, should not be seen. Nuclear pleomorphism can be found in up to 10% of Inverted Schneiderian papillomata (ISP). Acute and chronic inflammatory cells are present within the epithelium and the stroma. Neutrophils may be present in the epithelium and may form microabscesses. The stroma may be edematous and may contain neutrophils, eosinophils, plasma cells and lymphocytes.
5-15% of cases of ISP are associated with malignancy. The most common carcinoma is squamous cell carcinoma but spindle cell, clear cell, high grade mucoepidermoid and sinonasal undifferentiated carcinoma have also been seen. Due to this risk, all tissue from resections from ISP should be examined microscopically.
Variants: Exophytic Schneiderian papilloma (ESP), Inverted Schneiderian papilloma (ISP), oncocytic Schneiderian papilloma (OSP).
ESP most often arises from the lower, anterior nasal septum and has little to no risk of malignancy. ISP most often arises from the lateral nasal wall near the middle turbinate-ethmoid sinus area. This tumor may then grow into the nasal cavity and/or the paranasal sinuses, making local invasion a serious problem. ISP may have focal exophytic growth, but the majority of the tumor mass extends inward into the soft tissue, replacing submucosal glands. OSP usually arises from the lateral nasal wall, similar to the ISP.
The epithelium of the ESP appears the same as the ISP but instead of growing inward, it grows outward in broad papillary structures. The oncocytic variant epithelium has areas of similar to ISP but also has large areas of oncocytic cells with abundant, pink, finely granular cytoplasm. Additionally, the thickness of the epithelium in an OSP is generally less than in ISP and ESP and the surface is generally lined by ciliated cells.
All of these lesions are non-keratinizing, however, ESP may have focal keratinisation if it becomes irritated or if it protrudes from the nasal cavity and becomes subject to the dry air.
Recurrence rates after surgical resection are up to 50-70%.
Differential Diagnosis: Nonkeratinizing squamous cell carcinoma, however, this is distinguished by widespread nuclear atypia and may have partially clear cytoplasm.
This Case: In this case, the inverted pattern of growth is easily identified. There are multiple cell layers present and there is no evidence of atypia. The surface of some areas is lined by ciliated cells (image B) or mucus cells (image C)Inflammatory cells are scattered through the mucosa and, focally, there are neutrophilic microabscesses (image C).