CRA22 YOUNG-ONSET PLEURAL MESOTHELIOMA FOLLOWING SHORT-TERM ASBESTOS EXPOSURE: DIAGNOSIS VIA PLEUROSCOPY

Nor Safiqah Sharil^1,2, Boon Hau Ng¹, Rose Azzlinda Osman¹, Hsueh Jing Low³, Nik Nuratiqah Nik Abeed¹, Andrea Yu-Lin Ban¹
1. Respiratory Unit, Department of Medicine, Faculty of Medicine, Universiti Kebangsaan Malaysia, Hospital Canselor Tuanku Muhriz, Kuala Lumpur, Malaysia.
2. Internal Medical Unit, Faculty of Medicine and Health Science, Universiti Sains Islam Malaysia, Nilai, Negeri Sembilan.
3. Department of Anesthesiology and Critical Care, Faculty of Medicine, Universiti Kebangsaan Malaysia, Hospital Canselor Tuanku Muhriz, Kuala Lumpur, Malaysia.

Introduction
Malignant pleural mesothelioma (MPM) is a rare, aggressive malignancy strongly associated with asbestos exposure, typically diagnosed after decades of latency in individuals over 60. Fewer than 5% of cases occur before age 50. Chrysotile, the most prevalent form of asbestos in Malaysia, remains a carcinogen despite its lower fibre potency. We report a case of early-onset MPM in a middle-aged man, diagnosed via pleuroscopic-guided biopsy, following a brief but intense exposure to asbestos.

Case report
A 44-year-old man presented with a two-month history of progressive dyspnea and cough. Respiratory examination revealed reduced breath sounds over the left hemithorax. Thoracic ultrasound demonstrated a hypoechoic pleural effusion with multiple pleural-based and diaphragmatic lesions. Diagnostic pleurocentesis revealed an exudative effusion, with negative results for mycobacteria and cytology. Pleuroscopy showed multiple large masses on the costoparietal pleura, visceral pleura, and diaphragm. Contrast-enhanced CT of the thorax revealed extensive nodular pleural thickening involving the left hemithorax, with the largest nodule measuring 5.8 × 5.8 × 6.0 cm, along with multiple subcentimeter mediastinal lymph nodes. Targeted pleural biopsies confirmed epithelioid mesothelioma, with immunohistochemistry positive for CK AE1/AE3, Calretinin, and CK7. Given the unusually short latency period, a germline BAP1 mutation is suspected, and genetic testing is underway. A PET-CT scan is planned to assess for contralateral nodal involvement.

Conclusion
This case was staged as IMIG stage III, based on pleural disease and contralateral lymphadenopathy. Management options include platinum–pemetrexed chemotherapy and immune checkpoint inhibitors (nivolumab/ipilimumab) for unresectable disease. The patient may be considered for pleurectomy/decortication depending on operability. This case is notable for its extremely short latency, which raises the possibility of a genetic predisposition. It underscores the importance of incorporating occupational history, maintaining a high index of suspicion for MPM even in younger patients, and utilising pleuroscopy as a crucial tool for early diagnosis and staging. The case also underscores the importance of public health vigilance in countries where chrysotile use remains prevalent.