Malignant tumors of the paranasal fossae and sinuses represent 0.2% to 0.8% of all malignant tumors in the body and 3% to 6% of other head and neck tumors. It is possible to distinguish 4 different histologic types of sinonasal malignant tumors: squamous carcinoma, adenocarcinoma, adenoid cystic carcinoma, and sinonasal undifferentiated carcinoma. According to the WHO classification, there are 2 main types of adenocarcinomas: intestinal-type (ITAC) and nonintestinal type. ITACs are generally connected with professional exposure to wood and leather dust. The metalloproteinase 9 (ADAM-9) is a type 1 transmembrane protein that has been associated with cancer development and metastases. Our case of poorly differentiated sinonasal ITAC showed moderate to strong cytoplasmic positivity for ADAM-9 in association with moderate membrane staining for c-erbB-2 oncoprotein. In our opinion, the expression of these proteins could explain the tumoral growth and together they could represent the most interesting targets when designing any tumor treatment scheme.