Recurrent Hemorrhagic Pleural Effusions in a Patient with Biopsy-Proven Extrapelvic Endometriosis Complicated by Streptococcus mitis Empyema

Introduction

Thoracic endometriosis syndrome (TES) is a rare manifestation of endometriosis involving functional endometrial tissue within the thoracic cavity, representing the most common site of extra-abdominopelvic disease. Manifestations include catamenial pneumothorax, hemothorax, hemoptysis, and pulmonary nodules, with right-sided involvement predominating. Diagnosis remains challenging because histopathologic confirmation is frequently absent: implants may be microscopic, inaccessible for biopsy, or obscured by chronic inflammation, yielding nondiagnostic cytology or tissue specimens, so diagnosis often relies on clinical history, imaging, surgical evaluation, and exclusion of alternative etiologies. We report a 35-year-old woman with biopsy-proven abdominal wall endometriosis and recurrent right-sided hemorrhagic pleural effusions who developed a Streptococcus mitis empyema, illustrating how superimposed infection can further complicate diagnosis and management of suspected TES.

Case Description

A 35-year-old nulligravid woman with biopsy-proven abdominal wall endometriosis presented with progressive dyspnea and recurrent right-sided pleural effusions. In 2023 she developed a painful periumbilical mass that worsened with menstruation; biopsy later in 2023 confirmed endometriosis, and she was found to have a large right pleural effusion, ascites, and splenic/portal vein thrombosis. MRI in 2024 confirmed a 2.8-cm umbilical endometrioma, surgically excised later in 2024, followed by leuprolide acetate and letrozole. Despite treatment, hemorrhagic pleural effusions recurred; thoracentesis in 2025 showed an exudative effusion with cytology negative for malignancy. A year later, she presented with worsening dyspnea and pleuritic chest pain; imaging showed near-complete opacification of the right hemithorax with compressive atelectasis. A chest tube yielded hemorrhagic fluid, again cytology-negative, and cultures grew Streptococcus mitis, confirming empyema. Given loculated collections and incomplete re-expansion, she underwent robotic-assisted VATS with decortication and pleurodesis; intraoperative findings showed dense fibrinopurulent adhesions without gross endometriotic implants, and pathology did not identify endometrial tissue. She improved postoperatively, completed targeted antimicrobial therapy, and was discharged with multidisciplinary follow-up across Infectious Diseases, Pulmonology, Thoracic Surgery, and Gynecology.

Discussion

Negative cytology and operative pathology do not exclude TES, as thoracic implants may be hormonally inactive or obscured by fibrosis; diagnosis therefore relies on integrating clinical history, imaging, operative findings, and prior extrathoracic histologic confirmation rather than a single modality [2,3]. The most distinctive feature of this case was culture-confirmed Streptococcus mitis empyema superimposed on recurrent hemorrhagic effusions, a complication rarely described alongside suspected TES [1-3]. Microbiologic confirmation appropriately prioritized surgical source control, but an acute infectious process should not prematurely end evaluation for an underlying chronic pleural disorder; the empyema likely represented a superimposed complication rather than a competing diagnosis. Long-term management required ongoing gynecologic follow-up given the substantial recurrence risk of advanced endometriosis. Thoracic endometriosis syndrome should remain in the differential diagnosis of recurrent hemorrhagic pleural effusions in reproductive-age women with known endometriosis, even absent histopathologic confirmation, as secondary bacterial infection may obscure the underlying disease process.