A 75-year-old man presents to the emergency department with a 4-month history of progressive dyspnea, dry cough, and chest pain. He denies hemoptysis, fever, or weight loss. Past medical history is significant for coronary artery disease, hyperlipidemia, and hypertension. He takes rosuvastatin, aspirin, and lisinopril. He has a 40-pack-year smoking history and quit 5 years ago. He is afebrile, heart rate is 68 beats/minute, and blood pressure is 157/80mmHg. Physical examination reveals clubbing of the fingers, decreased breath sounds over the right lower lung field, and no lymphadenopathy. A chest CT scan shows a 3 cm pleural-based mass in the right lower lobe with adjacent pleural thickening. A biopsy of the mass reveals spindle-shaped cells with positive staining for calretinin and WT-1.
A) Malignant pleural mesothelioma
The patient’s smoking history, progressive dyspnea, chest pain, clubbing, and CT findings of a pleural-based mass with thickening, combined with biopsy showing spindle cells positive for calretinin/WT-1, indicate malignant pleural mesothelioma. This is strongly associated with asbestos exposure (even without smoking), affecting pleural mesothelial cells, with spindle cell histology in sarcomatoid subtypes.
Answer choice B: Metastatic adenocarcinoma, is incorrect. Metastatic adenocarcinoma may involve the pleura but shows glandular histology with primary site markers (e.g., TTF-1 for lung), not calretinin/WT-1 positivity.
Answer choice C: Non-small cell lung carcinoma, is incorrect. Non-small cell lung carcinoma (e.g., adenocarcinoma, squamous cell) arises from lung parenchyma, not pleura, and shows glandular/squamous histology and is negative for calretinin/WT-1.
Answer choice D: Pulmonary hamartoma, is incorrect. Pulmonary hamartoma is a benign, well-circumscribed parenchymal lesion with cartilage/fat on biopsy, not pleural-based or spindle cell histology.
Answer choice E: Pulmonary tuberculosis, is incorrect. Tuberculosis typically presents with fever, weight loss, hemoptysis, and cavitary lesions on CT. Biopsy shows caseating granulomas, not spindle cells or mesothelial markers.
Key Learning Point
Malignant pleural mesothelioma, linked to asbestos and often tobacco use, presents with pleural-based masses, dyspnea, and chest pain. Biopsy with calretinin/WT-1 positivity confirms the diagnosis.
