Abstract Malignant pleural mesothelioma, the most common primary tumor of the pleura, presents a significant diagnostic challenge due to its rarity and nonspecific symptoms. The vast majority of patients have had chronic occupational or environmental exposure to asbestos fiber. Surgical biopsy with extensive workup is usually required to rule out other disease processes and determine pathological subtype. We present the case of a 59-year-old Mexican-born male, without past medical history, who presented with eight months of progressive dyspnea and weight loss. He denied chest pain or pleurisy. He is a lifelong nonsmoker and worked in construction in Mexico and the United States. Computed tomography scan of his chest revealed a large right pleural effusion with diffuse nodular pleural thickening, interlobular septal thickening and lymphadenopathy. Repeat thoracentesis demonstrated exudative pleural fluid with negative cytology. He was admitted for expedited workup and concern for pleural tuberculosis given his migration history. He underwent pigtail chest tube placement with lytic installation, followed by video-assisted thoracoscopic surgery for decortication and pleural biopsy. Thoracoscopy revealed thick, adherent pleura with multiple loculated fluid collections. Histology revealed ill circumscribed spindle cell proliferation with moderate cytologic atypia in a background of fibrocollagenous tissue. Immunohistochemistry was nonspecific but suggestive of mesothelial lineage. Fluorescence in situ hybridization analysis demonstrated a 76% homozygous deletion of CDKN2A/B, a tumor suppressor gene, supporting a diagnosis of pleural sarcomatoid mesothelioma with desmoplastic features. This case exemplifies the challenges faced in diagnosing malignant pleural mesothelioma. Diagnostic evaluation and treatment requires a multidisciplinary team approach. Pleural sarcomatoid mesothelioma with desmoplastic features carries a poor prognosis and is particularly difficult to diagnose pathologically due to the haphazard nature of the spindle cells in dense stroma. Therefore, immunohistologic evaluation is often required to establish cell lineage and rule out other pleural based diseases such as fibrosing pleuritis. Both clinical and pathological findings are nonspecific, thus requiring additional testing to uncover the underlying diagnosis. Markers specific for malignant mesothelial proliferation are essential in establishing both the diagnosis and prognosis. This abstract is funded by: na
Swartzman et al. (Fri,) studied this question.