Abstract Introduction Fibrosing mediastinitis (FM) is a rare condition marked by excessive fibrous tissue in the mediastinum, often resulting from granulomatous infections such as Histoplasma capsulatum or Mycobacterium tuberculosis. While clinical features vary depending on the structures involved, pleural effusion is an uncommon manifestation that may mimic malignancy or infection, complicating timely diagnosis. Case Description An 18-year-old African American female with spina bifida was transferred from an outside hospital for evaluation of a suspected malignant pleural effusion. She reported a one-week history of a non-productive cough and orthopnea. Review of systems was otherwise unremarkable. On presentation, vital signs were within normal limits on room air. Laboratory evaluation revealed elevated inflammatory markers (ESR 34 mm/hr, CRP 9.15 mg/dL) with otherwise normal blood counts and electrolytes. Chest radiograph and CT imaging showed an anterior mediastinal mass, mediastinal lymphadenopathy, and a right pleural effusion with mild compressive atelectasis (Figure 1a-1b). Thoracentesis demonstrated lymphocyte-predominant exudative pleural fluid, with negative cytology and cultures. Endobronchial ultrasound (EBUS)-guided transbronchial needle aspiration revealed lymphoid tissue but was non-diagnostic. Cardiothoracic surgery was consulted and performed a right anterior thoracotomy with biopsy of the pleura and mediastinal mass. Histopathology showed dense fibrotic tissue with chronic inflammatory infiltrates, consistent with FM (Figure 1c-1d). The patient remained hemodynamically stable throughout hospitalization. Her postoperative course was uncomplicated; the chest tube was removed without difficulty, and she was discharged in stable condition with plans for outpatient follow-up. Discussion FM is a rare disorder characterized by excessive fibrous proliferation within the mediastinum, most commonly associated with prior Histoplasma capsulatum infection. Diagnosis is often delayed due to nonspecific symptoms and radiologic findings that may resemble malignancy or infection. While FM typically presents with airway or vascular compression, pleural effusion is an uncommon finding, generally associated with thoracic duct or great vessel obstruction. In the absence of these (as in this case), effusion is atypical and may complicate the diagnostic process. Although EBUS is frequently used for mediastinal sampling, it has limited yield in FM due to the paucity of viable tissue. When initial evaluations are non-diagnostic, surgical biopsy remains the most definitive diagnostic tool. FM should be considered in the differential diagnosis of mediastinal masses accompanied by pleural effusion, particularly when cytology and cultures are negative. Early histopathologic confirmation is essential to differentiate FM from other causes of mediastinal disease and to guide appropriate management. This abstract is funded by: None
Sheikh et al. (Fri,) studied this question.