Immunohistochemical distinction of intestinal-type sinonasal adenocarcinoma from metastatic adenocarcinoma of intestinal origin

Objectives: Distinction of intestinal-type sinonasal adenocarcinoma (ITAC) from adenocarcinoma of intestinal origin metastatic to the sinonasal cavity may be extremely difficult on histologic grounds alone. We studied the role of cytokeratin (CK) and mucin (MUC) expression in differentiating ITAC, metastatic adenocarcinoma of intestinal origin, and non-intestinal-type sinonasal adenocarcinoma (non-ITAC). Methods: We stained specimens from 5 cases of ITAC and 4 cases of non-ITAC, along with 4 colonic and 3 duodenal adenocarcinoma controls, with CK7 and CK20, MUC2 and MUC5, neuron-specific enolase (NSE), chromogranin (CHR), and carcinoembryonic antigen (CEA) in order to examine the possible combinations of markers that best aid in the diagnosis of these lesions. We also performed a retrospective review of our clinical experience with these rare lesions. Results: CK7 staining was positive in all ITAC and non-ITAC cases, whereas all cases displaying gastrointestinal-type differentiation (ITAC and metastatic intestinal cases) stained positive for both CK20 and MUC2. Staining for MUC5, NSE, CHR, and CEA was variable. Conclusions: Tumors with the CK7⁺, CK20⁺, MUC2⁺ immunophenotype are likely primary sinonasal lesions, whereas tumors with the CK7^-, CK20⁺, MUC2⁺ profile warrant further clinical evaluation to exclude metastatic disease from the gastrointestinal tract. Complete surgical resection of ITAC remains the mainstay of therapy.