OBJECTIVE The WHO 2005 histological classification separates sinonasal adenocarcinoma (ADC) into three classes: intestinal-type adenocarcinoma (ITAC), low-grade sinonasal ADC and high-grade sinonasal ADC. The goal of this study was to check the relevance of this classification on the prognosis of patients treated for ADC. METHODS All the files of patients treated consecutively in the ENT department of the Montpellier University Hospital for ADC between 1980 and 2003 were retrospectively re-examined. Each case was reviewed for anatomical and pathological data based on the immunohistochemistry results according to the WHO 2005 classification, with a study of a panel of markers: cytokeratin 7 (CK7), cytokeratin 20 (CK20), Villin, CDX2 and EGFR. The epidemiologic data, the methods of treatment and the follow-up were studied. The survival probabilities were calculated using the Kaplan-Meier method and the survival graphs were compared using a log-rank test. RESULTS Sixty-two files were reviewed. Twelve patients were reclassified into the adenoid cystic carcinoma category and excluded from the study. In the 50 remaining cases, there were 36 ITAC cases, four low-grade ADC cases and 10 high-grade dedifferentiated carcinomas. For all of the ADC cases, the total survival at 5 years and without recurrence was 64 and 52%, respectively. The analysis of the three subgroups showed a total survival of 72.2% for ITAC, 100% for low-grade and 20% for high-grade ADC with a significant difference (p=0.044). This immunohistochemical distinction was mainly based on the expression of CK20 found in 98% of the ITAC cases and absent in low- and high-grade ADC patients. CONCLUSIONS The WHO 2005 classification for sinonasal ADC provides a valuable prognosis by showing a difference in the progression profile between ITAC, low-grade ADC and high-grade ADC. Moreover, broader studies should be conducted to investigate the different subtypes of ITAC.