Respiratory adenomatoid hamartoma must be suspected on CT-scan enlargement of the olfactory clefts.

Objective: To demonstrate that Respiratory Epithelial Adenomatoid Hamartoma (REAH) of the nose, a recently individualized benign tumour, is characterized by a significant widening of the CT-scan width of the olfactory clefts.

Patients And Methods: Retrospective study comparing, in the axial and coronal planes, the CT-scan maximum width of the olfactory clefts, i.e. the maximum distance between both turbinal ethmoidal walls, of 15 REAH patients, 36 Nasal Polyposis (NPS) and 49 normal individuals.

Results: In axial and coronal planes, respectively, the medians of the olfactory clefts width were of 12.2 mm and 12.1 mm for REAH, and 5.6 mm and 5.4 mm for NPS, compared to 4.5 mm and 4.2 mm for normal individuals (both p < 0.0001). Total nasal width (i.e. the distance between both medial orbital walls) was not found to be different between groups in both planes. The median ratios "olfactory cleft width/total nasal width" were, for the axial and coronal planes respectively, of 53.1% and 44.7 for REAH, and 23.5% and 22.9% for NPS, compared to 19.2% and 19.1% for normal controls (both p < or = 0.001).

Conclusion: Compared to normal and nasal polyposis CT-scans, REAH significantly enlarges the olfactory clefts width. Bilateral REAH represent a genuine differential diagnosis of Nasal Polyposis; the CT-scan appears as a major clue to differentiate the two diseases. Endoscopic surgery of REAH definitely confirms their origin in the olfactory cleft, and opens a new field of endoscopic surgery of the olfactory cleft.