Low grade glandular lesions of the sinonasal tract: a focused review.

The sinonasal tract is a complex anatomic site with an exhaustive list of possible diagnoses. While most biopsies or resections encountered routinely consist of common diagnoses such as inflammatory polyps and papillomas, occasional cases are more difficult, and separating reactive or benign from malignancy can be challenging. One of the most poorly understood and daunting categories is low grade glandular or tubular proliferations, particularly on small biopsies. Possible diagnoses such as reactive lesions, respiratory epithelial adenomatoid hamartoma (REAH), seromucinous (glandular) hamartoma (SH) and low grade sinonasal adenocarcinomas (LGSNAC) must be entertained. REAH is composed of respiratory epithelial lined submucosal glands with variable connection to the surface and periglandular hyalinization. SH is a tubular proliferation reminiscent of normal serous glands which may be associated with REAH. LGSNAC is a diverse group of bland tubular and/or papillary tumors, which have a recurrence potential but an as yet uncertain potential for metastasis or mortality. The management for these lesions can be vastly different and conservative management is preferable, making this distinction more than academic. However, complicating this category are controversies surrounding their nature as reactive lesions versus neoplasms, the histologic and immunohistochemical overlap, and possible precursor relationships between some of them.