Abstract Introduction Malignant mesothelioma (MM) is an aggressive malignancy arising from pleural mesothelial cells, strongly associated with asbestos exposure. Diagnosis is often delayed due to nonspecific symptoms. Pleural fluid cytology has limited sensitivity for diagnosing mesothelioma, with sensitivity around 29% , much lower than for other thoracic malignancies (1).We present an unusual case of MM in a patient without asbestos exposure, diagnosed via right hilar (10R) lymph node biopsy and left upper lobe nodule sampling after a negative pleural effusion study. Systemic lymphadenopathy as an initial manifestation is exceedingly rare (2), underscoring the diagnostic challenges of atypical mesothelioma presentations. Case Presentation A 65-year-old male with chronic tobacco and intravenous methamphetamine use presented with progressive dyspnea and nonproductive cough for one week. Chest radiograph revealed complete opacification of the left hemithorax, and ultrasound confirmed a large pleural effusion. Thoracentesis yielded 1.5 L of exudative, lymphocyte-predominant fluid; however, cytology was negative for malignancy. CT imaging demonstrated a left hilar mass with mediastinal adenopathy, pleural nodularity, and lymphangitic spread, along with a left upper lobe nodule. Flexible bronchoscopy with endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) was performed. Cytology from the right hilar lymph node and left upper lobe biopsy revealed epithelioid malignant mesothelioma Immunohistochemistry showed positivity for CK7, calretinin, CK5/6, and WT-1, confirming the diagnosis. Post-procedure, the patient developed a left pneumothorax with a persistent air leak consistent with bronchopleural fistula, managed with fibrin sealant, autologous blood patch, and pigtail catheter with Heimlich valve. The patient was discharged with outpatient oncology follow-up. Discussion Malignant mesothelioma (MM) is a rare, aggressive malignancy arising from the pleura, with a global age-standardized incidence of approximately 0.3-0.43 per 100,000 persons. It predominantly affects older males due to historical occupational asbestos exposure, with incidence peaking in individuals over 80 years of age. (3) Our patient had no known exposure, highlighting the disease can arise without traditional risk factors. Diagnosis is challenging due to nonspecific symptoms and low pleural fluid cytology sensitivity (∼29%). In our case, cytology was negative, and diagnosis was made via lymph node biopsy and lung nodule sampling, an atypical and rare presentation with systemic lymphadenopathy. Overall, lymph node involvement in malignant mesothelioma is relatively uncommon, which distinguishes its behavior from other thoracic malignancies like lung cancer. (4) This case underscores the need for novel therapeutic strategies targeting molecular pathways, improved early detection, and identification of predictive biomarkers to guide treatment, ameliorate outcomes, and overall survival. This abstract is funded by: None
Latchman et al. (Fri,) studied this question.