A 33-year-old woman with known tuberous sclerosis complex presents with progressive exertional dyspnea and a left chylothorax. HRCT shows diffuse round, thin-walled cysts replacing normal parenchyma. Lung biopsy demonstrates proliferation of atypical spindle and epithelioid smooth muscle cells that stain positively with HMB-45. The diagnosis is:
- A Lymphangioleiomyomatosis ✓
- B Pulmonary Langerhans cell histiocytosis
- C Birt-Hogg-Dube syndrome
- D Lymphocytic interstitial pneumonia
Explanation
Lymphangioleiomyomatosis affects almost exclusively women, often in the setting of tuberous sclerosis, and features neoplastic smooth muscle proliferation around airways, vessels, and lymphatics, producing thin-walled cysts and chylothorax from lymphatic obstruction. The cells are perivascular epithelioid cells expressing melanocytic markers such as HMB-45, a staining profile unique among these options. Langerhans cell histiocytosis gives irregular cysts and nodules in smokers with CD1a-positive cells, and Birt-Hogg-Dube is an FLCN-related disorder with basal lower-lobe cysts and renal tumors.
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.