**4.2 Schneiderian papillomas**

This is the second important differential diagnosis of REAHs.

Schneiderian papillomas are benign epithelial neoplasms of the sinonasal tract. Their annual incidence ranges between 0.2 and 1.5/100,000 people per year.

They are classified in three types: exophytic/fungiform papilloma, endophytic/ inverted papilloma, and oncocytic/cylindrical cell papilloma. The inverted type is

**4.1 Inflammatory polyps**

*Sino-Nasal and Olfactory System Disorders*

are the location and their gross appearance.

with REAHs.

**Figure 6.**

**Figure 7.**

**56**

*Macroscopic and endoscopic view of a nasal polyp.*

Inflammatory polyps are certainly the most common lesions that are confused

The most notable clinical differences between REAHs and inflammatory polyps

Inflammatory polyps are typically the clinical manifestation of a sinonasal polyposis. Nasal polyps are rarely isolated. They are multiple and bilateral and usually extrude from the middle and superior meati. They are rarely attached to the

Nasal polyps are usually edematous and not indurated. On microscopy, both lesions can show fibroblastic and vascular proliferation, stromal edema, a mixed inflammatory cell infiltrate, and seromucinous gland proliferation. However, inflammatory polyps do not have florid adenomatoid proliferation and stromal

*Endoscopic view: right and left nasal cavity: presence of nasal polyps in the middle and superior meati.*

posterior septum. REAHs originate specifically from the olfactory cleft.

hyalinization which, when present, favor REAHs (**Figures 6–9**).

the most common, accounting for nearly two thirds of the cases. We limit the description to this type.

It is mostly unilateral. It occurs mainly in adults during the fifth or sixth decade. There is a predilection for men.

or respiratory type. The endophytic growth of squamous epithelium is not seen in REAH. Transmigrating neutrophils and neutrophilic microabscesses may be seen. Occasional mitoses may be seen in the basal layer. Mild to moderate atypia may be seen. Edema or chronic inflammatory infiltrate is present in the stroma

*REAHs and REAH-Like Lesions: Underdiagnosed lesions Often Misconfused with Nasal Polyps*

*Low magnification: typical view of an IP: it shows an endophytic growth pattern consisting of markedly thickened squamous epithelial proliferation growing downward into the underlying connective tissue stroma to form large clefts, ribbons, and islands. Note the absence of mucoserous glands. Delicate basement membrane.*

*Immunohistochemistry: high power shows the epithelium to be composed of pseudostratified columnar cells/*

(**Figures 11–13**).

*DOI: http://dx.doi.org/10.5772/intechopen.90327*

**Figure 11.**

**Figure 12.**

**59**

*positivity of MIB1 in the basal cells.*

Unlike inflammatory polyps and REAHs, inverted papillomas are considered true neoplasms. While REAHs tend to be located medial to the turbinate lamella, inverted papillomas have a predilection for the lateral wall of the nasal cavity or the paranasal cavities. Maxillary and ethmoid sinuses are the most common origins followed by the sphenoid and frontal sinuses. Even if inverted papillomas are benign histologic lesions, clinically they may be aggressive with a relatively strong potential for local destruction, high rate of recurrence (more or less 50%), and a risk of carcinomatous evolution. This transformation in squamous cell carcinoma can be synchrone or metachrone and more likely in case of recurrence. This malignant transformation has never been observed in the case of REAHs.

Human papilloma virus seems to be implicated in the pathogenesis of inverted papillomas. Chronic inflammation seems to be a favorizing factor in REAHs.

The treatment of inverted papilloma requires a more extensive and radical excision with a subperiosteal dissection and a drilling of the base of implantation. Endonasal medial maxillectomy is the golden standard for maxillary sinus origin. Recurrence is more likely in frontal sinus papillomatosis due to the localization and the difficulty to completely eradicate the lesion. The surgical treatment for REAHs is a complete excision without ethmoidectomy.

Grossly, inverted papilloma looks like a reddish-gray lobulated tumor, more firm than an inflammatory polyp, with a fairly characteristic "raspberry" aspect (**Figure 10**).

Histologically inverted papillomas have an endophytic growth pattern. There is an invagination of stratified squamous epithelium with an admixture of mucin containing cells and microcysts. The epithelium may be of squamous, transitional,

**Figure 10.** *Endoscopic view of an inverted papilloma originating from the left maxillary sinus.*

*REAHs and REAH-Like Lesions: Underdiagnosed lesions Often Misconfused with Nasal Polyps DOI: http://dx.doi.org/10.5772/intechopen.90327*

or respiratory type. The endophytic growth of squamous epithelium is not seen in REAH. Transmigrating neutrophils and neutrophilic microabscesses may be seen. Occasional mitoses may be seen in the basal layer. Mild to moderate atypia may be seen. Edema or chronic inflammatory infiltrate is present in the stroma (**Figures 11–13**).

#### **Figure 11.**

the most common, accounting for nearly two thirds of the cases. We limit the

transformation has never been observed in the case of REAHs.

*Endoscopic view of an inverted papilloma originating from the left maxillary sinus.*

is a complete excision without ethmoidectomy.

It is mostly unilateral. It occurs mainly in adults during the fifth or sixth decade.

Unlike inflammatory polyps and REAHs, inverted papillomas are considered true neoplasms. While REAHs tend to be located medial to the turbinate lamella, inverted papillomas have a predilection for the lateral wall of the nasal cavity or the paranasal cavities. Maxillary and ethmoid sinuses are the most common origins followed by the sphenoid and frontal sinuses. Even if inverted papillomas are benign histologic lesions, clinically they may be aggressive with a relatively strong potential for local destruction, high rate of recurrence (more or less 50%), and a risk of carcinomatous evolution. This transformation in squamous cell carcinoma can be synchrone or metachrone and more likely in case of recurrence. This malignant

Human papilloma virus seems to be implicated in the pathogenesis of inverted

Grossly, inverted papilloma looks like a reddish-gray lobulated tumor, more firm than an inflammatory polyp, with a fairly characteristic "raspberry" aspect

Histologically inverted papillomas have an endophytic growth pattern. There is an invagination of stratified squamous epithelium with an admixture of mucin containing cells and microcysts. The epithelium may be of squamous, transitional,

papillomas. Chronic inflammation seems to be a favorizing factor in REAHs. The treatment of inverted papilloma requires a more extensive and radical excision with a subperiosteal dissection and a drilling of the base of implantation. Endonasal medial maxillectomy is the golden standard for maxillary sinus origin. Recurrence is more likely in frontal sinus papillomatosis due to the localization and the difficulty to completely eradicate the lesion. The surgical treatment for REAHs

description to this type.

(**Figure 10**).

**Figure 10.**

**58**

There is a predilection for men.

*Sino-Nasal and Olfactory System Disorders*

*Low magnification: typical view of an IP: it shows an endophytic growth pattern consisting of markedly thickened squamous epithelial proliferation growing downward into the underlying connective tissue stroma to form large clefts, ribbons, and islands. Note the absence of mucoserous glands. Delicate basement membrane.*

#### **Figure 12.**

*Immunohistochemistry: high power shows the epithelium to be composed of pseudostratified columnar cells/ positivity of MIB1 in the basal cells.*

On microscopy, papillary and colonic types are the most common architectures.

Differentiating ITAC from REAH is usually not difficult as the cell types, highgrade features, and increased mitotic index are characteristics for ITAC. ITAC is

*REAHs and REAH-Like Lesions: Underdiagnosed lesions Often Misconfused with Nasal Polyps*

*Intestinal-type adenocarcinoma: Immunohistochemistry—Positivity for CK20, CK7, and MIB1.*

*LGSNAC: Glandular proliferations lined by cuboidal to columnar cells which are usually monomorphic and*

positive for CK20 and MIB1 and negative for CK7 (**Figure 14**).

*DOI: http://dx.doi.org/10.5772/intechopen.90327*

**Figure 14.**

**Figure 15.**

**61**

*cytologically bland.*

**Figure 13.** *Immunohistochemistry: high power/positivity of CK7.*
