Answer: Sinonasal adenocarcinoma, low grade

Histology: The submucosa is filled by a non-encapsulated tumor comprised of crowded back-to-back small glands without an intervening stroma. The glands are lined by a single layer of non-ciliated cuboidal cells with only mild cellular pleomorphism. These glands appear to arise directly from the overlying ciliated epithelium. Basophilic cytoplasmic granules are not identified.

Discussion: Adenocarcinomas of the sinonasal tract arise from either the seromucinous glands in the submucosal or from the surface epithelium. Those tumors that can be readily recognized as a specific subtype of salivary gland carcinoma (e.g. acinic cell carcinoma, adenoid cystic carcinoma, etc…) should be designated accordingly. For those adenocarcinomas that do not neatly fit into any specific subtype of salivary gland carcinoma, primary origin from the surface epithelium should be considered.

Sinonasal adenocarcinomas of surface epithelial origin fall into two categories: intestinal and non-intestinal types. Intestinal sinonasal adenocarcinomas histologically resemble normal or malignantly transformed intestinal epithelium. These tumors are associated with prior exposure to wood dust, and they tend to be aggressive neoplasms. The non-intestinal sinonasal adenocarcinomas do not histologically resemble normal or transformed intestinal epithelium. That being said, this group consists of a heterogeneous mix of tumors demonstrating any combination of papillary and glandular growth.

Most of these non-intestinal sinonasal adenocarcinomas are well differentiated (i.e. low-grade sinonasal adenocarcinoma). The distinction between the various types of adenocarcinomas involving the sinonasal tract is prognostically important. The low-grade sinonasal adenocarcinomas, for example, are associated with an excellent prognosis in contrast to the dismal prognosis associated with the intestinal sinonasal adenocarcinomas.