Answer: Sinonasal adenocarcinoma, intestinal type

Histology: The overlying squamous mucosa is ulcerated but without dysplasia. The submucosa is infiltrated by adenocarcinoma growing as glands, elongated papillary fronds and cribriform structures. These structures are lined by mitotically active stratified columnar cells with associated cellular necrosis.

Discussion: While most adenocarcinomas involving the palate are derived from the minor salivary glands that densely populated this site, adenocarcinomas of non-salivary origin can infrequently involve this site-either by direct local extension from the maxillary sinus (i.e. sinonasal adenocarcinoma) or metastatic spread from some non-head and neck site. The distinctly colonic appearance of this particular tumor is quite characteristic of the intestinal type of sinonasal adenocarcinoma. The adenocarcinomas may demonstrate a range of histologic grades (from well differentiated papillary neoplasms to poorly differentiated signet ring cell carcinomas), but most resemble conventional gland-forming colorectal adenocarcinomas. In fact, this resemblance is so striking that the diagnosis of metastatic colorectal carcinoma should be addressed on clinical grounds. Salivary duct carcinoma is a high grade adenocarcinoma of salivary origin. In contrast to intestinal-type sinonasal adenocarcinomas, salivary duct carcinomas are comprised of cells with abundant pink cytoplasm and closely resemble ductal carcinoma of the breast in their microscopic appearance.

Intestinal-type sinonasal adenocarcinomas are locally destructive tumors with a propensity to locally recur. Complete surgical removal is the treatment of choice. The disease can have a protracted course necessitating lifetime follow-up of these patients.