Due to the vast majority of pathologies that could arise in the maxillary sinus, some pathologies with clinical significance cannot be considered as either malignant or benign. Some of these are silent sinus syndrome, maxillary sinus agenesis, missed maxillary sinus ostium syndrome, maxillary sinus fracture, maxillary sinus foreign body and oroantral fistula. Silent sinus syndrome (SSS), also known as imploding antrum syndrome, is a very rare condition, usually represented by asymptomatic spontaneous collapse of the sinus walls and floor of the orbit. This is while maxillary sinus agenesis refers to the lack of maxillary sinus due to the absence of its primordial tissue. Furthermore, missed maxillary sinus ostium syndrome refers to a phenomenon that occurs when the ostium of the maxillary sinus is missing. Lastly, an oroantral fistula is an unnatural communication present between the oral cavity and the maxillary sinus.