Answer: Glandular hamartoma

Histology: The specimen consists of a polypoid fragment of respiratory mucosa with stromal collagenization and focal submucosal. There is a downward proliferation of glands that are lined by ciliated respiratory epithelium. They appear to take origin from the surface epithelium. Although the glands are branching, they do not demonstrate a complex glandular growth or a back-to-back growth pattern, and they are separated by stromal tissues. Smaller seromucinous-type glands percolate through the stroma between the larger open glands and extend deeply between the bony fragments. On close inspection, the glands appear to be surrounded by a thin myoepithelial layer.

Discussion: Inflammatory sinonasal polyps are histologically characterized by submucosal edema, an inflammatory infiltrate that includes numerous eosinophils, and by a glandular proliferation. The glandular component is rarely conspicuous, but in those exceptional cases where the gland proliferation is florid and eye-catching, a simple inflammatory sinonasal polyp may be easily confused with a low-grade sinonasal adenocarcinoma. Such lesions are sometimes referred to as hamartomas of the sinonasal tract, a term that emphasizes the florid but self-limited proliferation of an endogenous tissue component. Hamartomas that are comprised of branching glands lined by respiratory epithelium are designated as “respiratory epithelial adenomatoid hamartomas (REAH)”. These branching structures are believed to take origin from the surface epithelium. Those hamartomas where the epithelial component is dominated by a proliferation of small seromucinous glands are designated as “glandular hamartomas”.

Unlike low-grade sinonasal adenocarcinomas, the glands sinonasal hamartomas are separated by stroma and do not demonstrate a complex back-to-back arrangement. Further, they demonstrate two cell layers (luminal cells and myoepithelial cells) in contrast to the single cell layer characterizing well differentiated sinonasal adenocarcinomas. Some believe that the development of sinonasal hamartomas is induced by an inflammatory process. Surgery is generally curative.