A patient complains about mobility of the 26, 27, 28 teeth, periodic pain, sensation of heaviness in the corresponding half of the upper jaw, haemorrhagic discharges from the left side of nose. These presentations have been observed for 4 months, within the last month the pain has become worse, the patient presents now with general weakness. Examination of the oral cavity reveals the grade II mobility of the 26, 27, 28 teeth. On palpation of the maxillary tuber, the bone wall was found to be absent. X-ray picture shows a homogeneous shadowing of maxillary sinus; bone structures have unclear contours. What is the most likely diagnosis?