Answer: Glandular hamartoma

Histology: The large polypoid mass is largely made up of a proliferation of acinar structures. These acinar structures lack cellular atypia, and they closely resemble the seromucinous glands normally dispersed throughout the sinonasal mucosa. The individual glands are not back-to-back, but instead are separated by fibroconnective tissues. Some of the glands are dilated and filled with eosinophilic secretions. The surface epithelium itself is not particularly proliferative.

Discussion: Glandular (seromucinous) hamartoma of the nasal cavity reflects an increase number of non-neoplastic seromucinous glands with formation of a polypoid mass in the nasal cavity. The seromucinous glands appear quite unremarkable at the cellular level, thus the pathologic alteration is solely quantitative and not qualitative. In contrast to inflammatory sinonasal polyps, the process is usually unilateral and unifocal; thus raising the clinical concern of some neoplastic process. This process should not be confused with a low grade sinonasal adenocarcinoma as the seromucinous glands maintain an outer layer of myoepithelial cells, and they lack atypia cytologically and a back-to-back arrangement architecturally. Glandular hamartomas differ from the more common respiratory epithelial adenomatoid hamartoma (REAH) in that the major contributor to the mass lesion is the seromucinous glandular component. In REAH, a proliferative surface epithelium gives rise to branching projects that fill the submucosal.

Not everyone accepts that hamartomas of the nasal cavity are truly hamartomatous. Some believe that they simply represent an exaggerated response stimulated by an inflammatory reaction (a predominant component of an inflammatory sinonasal polyp). Others suggest that they may in fact represent a benign neoplasm. Whatever the true nature of these lesions, they are benign and do not recur following complete excision.