Powdr Room Vent

I am putting a powder room in my basement - toilet and sink only. I am using a combo light and vant fan fixture. It is a drop ceiling. To save time and money I planned to only vent above the ceiling and not outside. Somoene I talked to mentioned that this setup could cause mold between the drop ceiling and floor joyces. I did not think it would be an issue given that I am not using a bath or shower moisture should be limited. Any advice here would be helpful.