108 Thoracic Endometriosis and Catamenial Pleural Effusion: A Diagnostic Dilemma

Introduction/Objective Thoracic endometriosis (TE) is characterized by endometrial tissue in the thoracic cavity, with symptoms typically manifesting during menstruation. The diagnosis remains challenging due to limited tissue samples, cautery, and inflammation. Timing of the biopsy during menstruation may improve detection of key histologic features. Methods/Case Report A 41-year-old female with uterine fibroids and ovarian cysts presented with multiple recurrent episodes of sharp pleuritic-type chest pain. Evaluation revealed a right exudative pleural effusion. The clinical differential diagnosis included malignancy, rheumatoid pleuritis, infection and pulmonary embolism. Extensive workup including multiple imaging modalities, rheumatologic and infectious workups failed to establish a diagnosis. A pleuroscopy with biopsy and pleural fluid cytology were performed, which showed non-specific inflammation and couldn’t establish the diagnosis either. Due to the cyclic nature of her symptoms, a repeat pleuroscopy was performed during her menses, which showed hyperpigmented nodules involving the pleura. This repeat biopsy demonstrated hemosiderin-laden macrophages, with a focus of endometrial-type glands and stroma, confirmed by ER and CD10 immunostains, establishing the diagnosis of thoracic endometriosis. Results NA Conclusion This case highlights that accurate diagnosis of TE relies on clinical-pathologic correlation and biopsy timing during menstruation. Awareness of symptom cyclicity and strategic specimen collection is essential to improve detection and patient outcomes.