P-235 * WHY DOES CATAMENIAL PNEUMOTHORAX CAUSE FREQUENT POSTOPERATIVE RECURRENCE?

Objectives: Surgery for catamenial pneumothorax (thoracic endometriosis: TE) is a partial resection of the diaphragm by video-assisted thoracoscopic surgery (VATS). But there is high postoperative recurrence rate (between 30 and 70%) in previous reports. The aim of this study was to clarify the cause of high postoperative recurrence. Methods: Sixty-six female patients with catamenial pneumothorax (CPT) underwent VATS. We tried a clinical classification of thoracoscopic and microscopic diagnosis for TE. ‘0’ is expressed as no endometriosis, ‘1’ is suspicious and ‘2’ is confirmed. Diaphragm is expressed as D, lung is L and thoracic parietal pleura is W, each for thoracoscopic diagnosis. They are expressed as d, l and w, each for microscopic diagnosis. We studied a developmental staging of TE inside the thoracic cavity. The a, b or c mean staging of microscopic diagnosis. The A, B or C mean staging of thoracoscopic diagnosis. Stage 0 is no endometriosis anywhere. Stages a or A are endometriosis just in the diaphragm. Stages b or B are endometriosis just in two parts of the diaphragm or lung or thoracic parietal pleura. Stages c or C are endometriosis in the diaphragm and lung and thoracic parietal pleura. Results: In VATS, Stage A: 18 cases (26%), Stage B: 33 cases (52%), Stage C: 13 cases (20%) each. In microscopic examination, Stage 0: 2 cases (3%), Stage a: 27 cases (44%), Stage b: 26 cases (42%) and Stage c: 7 cases (11%) each. Gland tissue of endometriosis in diaphragm is 21 cases (33%) and stromal tissue of endometriosis in diaphragm is 58 cases (91%). Most of TE besides diaphragm is at the back side of the thoracic parietal pleura and at the margin of the middle lobe (S4) or lower lobe (S6). Conclusions: Forty--six (72%) cases of TE are in stage B or C at surgery. Dissemination to intra-thoracic cavity is already visible at surgery. That is the cause of high postoperative recurrence. Stromal tissue is important for microscopic diagnosis on TE. Disclosure: No significant relationships.