A 33-year-old woman presents with progressive dyspnea and recurrent unilateral pleural effusions that are chylous on analysis. HRCT shows diffuse thin-walled round cysts throughout the lungs with normal intervening parenchyma. She has no history of smoking. The underlying lesion is characterized by:
- A CD1a-positive dendritic cells forming stellate nodules in bronchioles
- B Proliferation of immature smooth muscle cells around airways and lymphatics expressing HMB45 ✓
- C Non-caseating granulomas along lymphatic routes
- D Lamellar hyaline membranes lining dilated alveolar ducts
Correct answer: B. Proliferation of immature smooth muscle cells around airways and lymphatics expressing HMB45
Explanation
Lymphangioleiomyomatosis, seen almost exclusively in women, often related to tuberous sclerosis complex, features proliferation of immature smooth muscle-like cells around airways, vessels, and lymphatics. These cells coexpress actin and the melanocytic marker HMB45. Airway obstruction produces the cysts, and lymphatic obstruction causes chylothorax. Stellate CD1a-positive nodules define pulmonary Langerhans cell histiocytosis, a smoking-related disease.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.