Abstract
Organized hematoma are benign and non-neoplastic lesions. However, a differential diagnosis using imaging findings from a malignant tumor are extremely difficult. We experienced a hyper-giant maxillary organized hematoma reaching to the other side of the maxillary sinus, which was endospopically treated. Many papers report extra sinus surgery for organized hematoma so as to avoid perioperative bleeding. However, it is possible to lose mass volume step by step in an operation process because organized hematoma are not solid neoplasms. We conclude that even if organized hematoma of the maxillary sinus are huge, they can be successfully treated by endoscopic sinus surgery under an accurate preoperative diagnosis and with careful surgical planning.