**1. Introduction**

REAH is the eponysm for Respiratory Epithelial Adenomatoid Hamartoma. It is a relatively new diagnosis, only added to the World Health Organization classification of tumors in 2005 [1].

Wenig and Heffner were the first to describe it in 1995 in a series of 31 cases [2]. They described it as "a proliferation of glands lined by multi-layered ciliated respiratory epithelium, often with admixed mucocytes, arising in direct continuity with the surface epithelium, which invaginated downward into the submucosa."

The lesion is usually diagnosed in middle-aged patients. Clinically it may manifest as a solitary lesion or in association with sinonasal polyposis. The former is far less common than the latter. The lesion takes its origin either in the olfactory cleft, the posterior septum, or the rhinopharynx [1–5] Because the incidence, clinical signs, imaging, modality of treatment, outcomes, and pathogenesis seem to be quiet different between these two clinical patterns, we call the first ones "REAHs" and the second ones "REAH-like." This terminology is proposed by Jankowski [3, 5] and Hawley [4] as well.

The purpose of this paper is to remind the histopathological characteristics and differential diagnosis of REAHs/REAH-like lesions and to report two different

cohorts of patients (one with REAHs and the other with REAH like lesions), treated in the ENT department of the CHU UCL Namur.
