**3. Immunohistochemistry of REAHs**

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 of it.

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 a high proliferation index.

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