Thoracic Endometriosis and Catamenial Pneumothorax: Imaging Pitfalls and an Integrated Diagnostic Approach.

Catamenial pneumothorax is a rare form of recurrent spontaneous pneumothorax occurring in women in temporal association with the menstrual cycle, most commonly within 72 h before or after the onset of menstruation, and is frequently encountered as part of thoracic endometriosis syndrome. Thoracic endometriosis represents an extrapelvic manifestation of endometriosis in which ectopic endometrial tissue may involve the pleura, diaphragm, lung parenchyma, or airways, leading to cyclic pleuropulmonary symptoms. The clinical spectrum includes catamenial pneumothorax, catamenial hemothorax, catamenial hemoptysis, and pulmonary endometriotic nodules. This narrative review critically analyzes the diagnostic challenges and limitations of imaging modalities in thoracic endometriosis, with particular emphasis on diagnostic delay, radiological pitfalls, and the discrepancy between morphological detection and etiological confirmation. Chest radiography and computed tomography are useful for documenting acute thoracic events, whereas magnetic resonance imaging may provide additional tissue characterization in selected cases, particularly when hemorrhagic or diaphragmatic lesions are suspected. However, imaging findings are often nonspecific, temporally variable, and insufficient to establish the diagnosis when interpreted in isolation. Recognition of thoracic endometriosis therefore requires correlation of imaging findings with menstrual cyclicity, gynecological history, clinical phenotype, and, when indicated, surgical and histopathological assessment. The available evidence remains limited by retrospective designs, small case series, inconsistent diagnostic criteria, and lack of validated thoracic-specific imaging pathways. Accordingly, an integrated clinical-radiological-surgical approach should be regarded as a pragmatic diagnostic framework rather than a validated algorithm. Such an approach may improve clinical suspicion, reduce diagnostic delay, and support more appropriate multidisciplinary management of this underrecognized condition.