Antral pseudocyst (AP) is a process formed by the inflammatory exudate accumulation below the sinuses mucous membrane and causing a sessile elevation. AP is a dome-shaped, well-delineate, faintly radiopaque lesion on the intact floor of the maxillary sinus. A case of AP with an unusual location is presented. A 24-year-old male was submitted to the panoramic radiographic exam and an around, well-defined, faintly radiopaque lesion was detected in the tuberosity extension of maxillary sinus. The differential clinical-radiograph diagnoses were AP, non-odontogenic cysts, odontogenic cysts, odontogenic and non-odontogenic tumours. Fine needle aspiration demonstrated presence of viscous yellow liquid. It was performed an excisional biopsy and the histological diagnosis was AP. It is necessary biopsy when this doubt persists and also emphasize the recognition of AP in other differential diagnose and management with other lesions in region of the maxillary sinus.