Simple SummaryPrognostic markers play an important role in the risk assessment and treatment of cancers in general. The aim of this systematic review was to assess the potential prognostic markers for the rare sinonasal intestinal-type adenocarcinoma. The results from this paper may help specialists to better understand the risks of this disease and provide more insight into the prognosis. We found twenty-one biomarkers. Whilst some had a significant negative effect on prognosis, none had a positive effect. Furthermore, the biomarkers found were analyzed within the hallmarks of cancer to provide more information considering the carcinogenesis of this carcinoma. This could help in the better treatment of sinonasal intestinal-type adenocarcinoma and better patient outcomes.AbstractOne of the rare tumor entities present in the nose and paranasal sinuses is sinonasal (non-) intestinal-type adenocarcinoma (ITAC/non-ITAC). Currently, surgery with postoperative radiotherapy is the cornerstone of the treatment of these tumors. Systemic treatment is usually applied in a palliative setting. The prognosis of these tumors is very diverse. Biomarkers that may have prognostic value in these rare malignancies could help clinicians in decision-making. A systematic search of the literature was performed using the PubMed database. All studies investigating the prognostic significance of biomarkers in paranasal sinus ITAC/non-ITAC were retrieved. The findings were categorized within the hallmarks of cancer, to gain an understanding of the functions of possible prognostic biomarkers in the development of ITAC/non-ITAC. There were twenty-one studies reporting on twenty-one possible biomarkers included in the review. The expression of Mucin antigen sialosyl-Tn, C-erbB-2 oncoprotein, TIMP3 methylation, TP53, VEGF, ANXA2, MUC1 and the mucinous histological subtype were found to have a significant negative effect on survival. None of the biomarkers were found to have a positive effect on prognosis. The hallmarks ‘activating invasion and metastasis’ and ‘sustaining proliferative signaling’ seem to play the largest role in sinonasal (non-)ITAC. It could be concluded that there are multiple biomarkers foreboding a negative prognosis for ITAC/non-ITAC patients.