Lymphangioleiomyomatosis
Key Facts
Terminology
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Lymphangioleiomyomatosis (LAM)
Etiology/Pathogenesis
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Unknown etiology
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May share similar genetic relationship with tuberous sclerosis complex
Clinical Issues
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Incidence
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More common in premenopausal women
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Rarely described in children
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Symptoms
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Cough
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Shortness of breath
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Chylous effusion
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Pneumothorax
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Hemoptysis
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Microscopic Pathology
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Cystic changes
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Spindle cell proliferation lining cystic structures
Top Differential Diagnoses
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Leiomyoma
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Usually forms a tumor mass
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Unusual for leiomyoma to present with prominent cystic changes
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Leiomyosarcoma
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LAM lacks atypia or mitotic activity
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Tuberous sclerosis
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Such distinction may not be possible on histologic grounds alone
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It is important to obtain a clinical history
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Low-power view of LAM shows 2 focal areas of muscle proliferation  . Note that the rest of the pulmonary parenchyma appears to be within normal limits. |
High-power magnification of LAM shows the classical presence of smooth muscle proliferation. The muscle proliferation is obvious and has obliterated the normal alveolar lining  . |
TERMINOLOGY
Abbreviations
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Lymphangioleiomyomatosis (LAM)
Synonyms
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Lymphangiomyomatosis
Definitions
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Nonneoplastic lung condition characterized by presence of immature muscle proliferation
ETIOLOGY/PATHOGENESIS
Etiology
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Unknown etiology
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May share similar genetic relationship with tuberous sclerosis complex
CLINICAL ISSUES
Epidemiology
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Incidence
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LAM occurs in approximately 2 cases per million patients
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May be underreported
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Age
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More common in premenopausal women
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Rarely described in children
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Gender
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Commonly affects women
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Presentation
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Cough
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Shortness of breath
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Chylous effusion
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Pneumothorax
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Hemoptysis
Treatment
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No specific treatment
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Hormonal manipulation
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Oophorectomy
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Lung transplantation
Prognosis
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Predominantly cystic lesions may have poor prognosis
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85% survival at 5 years
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70% survival at 10 years
IMAGE FINDINGS
General Features
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Bilateral multiple nodular and cystic changes in lung parenchyma
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Unilateral involvement is also possible
MACROSCOPIC FEATURES
General Features
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Multiple cysts with honeycomb appearance
MICROSCOPIC PATHOLOGY
Histologic Features
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Cystic changes
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Hemorrhage
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Spindle cell proliferation
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In alveolar walls
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Lining cystic structures
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With focal clear cell change
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Lacking atypia or mitotic activity
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Adjacent lung parenchyma may show type II pneumocyte hyperplasia
Predominant Pattern/Injury Type
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Cystic
Predominant Cell/Compartment Type
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Smooth muscle
DIFFERENTIAL DIAGNOSIS
Leiomyoma
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Usually forms a tumor mass
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