Catamenial pneumothorax is definitely linked to one aspect of endometriosis. But there are two distinct routes of spread of endometrial tissue to the thorax. The first, by far the most common, is the transperitoneal route from the pelvis to the diaphragm, which accounts for diaphragmatic pores and catamenial pneumothorax. The other, quite rare, is the hematogenous route, by which uterine endometrial tissue and/or decidua literally “metastasize” to the lung via the venous system, which drains the uterus. In this latter instance, the result is the appearance of pulmonary nodules or deposits, which are clinically manifested by hemoptysis, not by pneumothorax or hemothorax. The pathologic examination of resected specimens proves them to be endometrial or decidual tissue metastatic to the pulmonary parenchyma. The monthly periodicity of catamenial hemoptysis, sometimes referred to as vicarious menstruation, is due to the cyclic hormonal activity of the metastatic endometrial nodule in the lung parenchyma.2–3
It does not cause catamenial pneumothorax.