**2. Histopathological characteristics of REAHs and REAH-like lesions**

Grossly, REAH looks like a "polypoid fleshy to firm mass with areas of induration." It is yellow or white [6]. It may have varying sizes (**Figures 1–3**).

The histologic picture is dominated by the presence of a glandular proliferation with a polypoid appearance. The proliferation starts from the surface epithelium and tends to be submucosal.

The glands are lined by ciliated respiratory epithelium originating from the surface respiratory epithelium. The glands are typically round to oval in shape and were small to medium in size with prominent dilation. Stromal tissue separates the glands. The epithelium may be cuboidal or flat, and mucinous gland metaplasia is often seen. Occasionally the gland lumina are filled with mucinous or eosinophilic amorphous material. It often demonstrates periglandular stromal hyalinization, and there is often a mixed inflammatory infiltrate within the stroma.

In the literature we can find another type of REAH called **COREAH**. It is characterized by a chondro-osseous differentiation. Flavin [7] and Roffman [8] were the two first authors to publish this entity, respectively, in 2005 and 2006. Since then 11 cases have been reported [9, 10]. It can occur in children or adults.

The histological features are almost exactly the same as REAH, but COREAH has islands of immature hyaline cartilage interspersed throughout the lesion (**Figures 4** and **5**).

**Figure 2.**

**Figure 3.**

*the stroma.*

**53**

*REAHs: The glandular proliferation arises in direct continuity with the surface epithelium with invagination*

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

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

*REAHs: Occasionally the gland lumina are filled with mucinous or eosinophilic amorphous material. It often demonstrates periglandular stromal hyalinization, and there is often a mixed inflammatory infiltrate within*

*downward into the submucosa. Clusters of seromucinous glands are seen.*

**Figure 1.** *Gross appearance of a REAH.*

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

#### **Figure 2.**

cohorts of patients (one with REAHs and the other with REAH like lesions), treated

**2. Histopathological characteristics of REAHs and REAH-like lesions**

tion." It is yellow or white [6]. It may have varying sizes (**Figures 1–3**).

there is often a mixed inflammatory infiltrate within the stroma.

Grossly, REAH looks like a "polypoid fleshy to firm mass with areas of indura-

The histologic picture is dominated by the presence of a glandular proliferation with a polypoid appearance. The proliferation starts from the surface epithelium

The glands are lined by ciliated respiratory epithelium originating from the surface respiratory epithelium. The glands are typically round to oval in shape and were small to medium in size with prominent dilation. Stromal tissue separates the glands. The epithelium may be cuboidal or flat, and mucinous gland metaplasia is often seen. Occasionally the gland lumina are filled with mucinous or eosinophilic amorphous material. It often demonstrates periglandular stromal hyalinization, and

In the literature we can find another type of REAH called **COREAH**. It is characterized by a chondro-osseous differentiation. Flavin [7] and Roffman [8] were the two first authors to publish this entity, respectively, in 2005 and 2006. Since then 11 cases have been reported [9, 10]. It can occur in children or adults. The histological features are almost exactly the same as REAH, but COREAH

has islands of immature hyaline cartilage interspersed throughout the lesion

in the ENT department of the CHU UCL Namur.

*Sino-Nasal and Olfactory System Disorders*

and tends to be submucosal.

(**Figures 4** and **5**).

**Figure 1.**

**52**

*Gross appearance of a REAH.*

*REAHs: The glandular proliferation arises in direct continuity with the surface epithelium with invagination downward into the submucosa. Clusters of seromucinous glands are seen.*

#### **Figure 3.**

*REAHs: Occasionally the gland lumina are filled with mucinous or eosinophilic amorphous material. It often demonstrates periglandular stromal hyalinization, and there is often a mixed inflammatory infiltrate within the stroma.*

**3. Immunohistochemistry of REAHs**

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

**4. Differential diagnosis of REAHs**

*REAHs: Immunohistochemistry: Positivity for CK7 and negativity for CK20.*

adenocarcinoma.

**55**

The differential diagnostic of REAHs concerns the inflammatory polyps, Schneiderian papillomas, seromucinous hamartoma, and low-grade non-intestinal

a high proliferation index.

of it.

Immunohistochemistry has not been used to an extensive degree in the diagnosis of REAH, and it is not absolutely necessary to use it to make the definitive diagnosis

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

However, Ozolek et al. did an immunohistochemical study in which they examined the profile of REAH [11]. REAHs are positive for CK7, negative for CK20 and CDX-2, and positive for MIB1 and Ki67. p63 staining was seen in the basal cells of REAH, which had a low proliferation index. The use of Mindbomb 1 (MIB-1) is useful in distinguishing REAH from other neoplasms, since neoplasms tend to have

#### **Figure 4.**

*COREAH: Nasal chondromesenchymal hamartoma. Multiple tumor fragments with a mucosal surface and nodules of cartilage (in red).*

#### **Figure 5.**

*Seromucinous hamartoma: The mass is covered by respiratory epithelium and is comprised of lobular or haphazard proliferations of small to large glands and ducts which are lined by a single layer of cuboidal or flattened epithelial cells.*

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