Lymphangioleiomyomatosis

Melissa L. Rosado-de-Christenson, MD, FACR

Key Facts

Terminology

Proliferation of atypical smooth muscle cells in lungs & lymphatics associated with pulmonary cysts

Imaging Findings

Radiography
- Normal or increased lung volumes
- Diffuse bilateral reticular opacities
HRCT
- Thin-walled air-filled pulmonary cysts diffusely distributed throughout lung

Top Differential Diagnoses

Pathology

Widespread interstitial infiltrate of immature short spindle cells resembling smooth muscle cells
Similar findings in TSC in which micronodular pneumocyte hyperplasia may also be present

Clinical Issues

Affects women of childbearing age who present with progressive dyspnea, pneumothorax, or chylothorax
Variable prognosis with median survival of 8-10 years after diagnosis

Diagnostic Checklist

Radiographs may appear normal or near normal
Patients presenting with pneumothorax may be misdiagnosed with primary spontaneous pneumothorax

Axial HRCT shows typical findings of LAM characterized by diffuse bilateral thin-walled air-filled pulmonary cysts

of uniform size, with small foci of intervening normal lung

Coronal HRCT shows the typical distribution of cysts in LAM. Although the upper lung cysts

are larger than those in the lower

, there is no preferential upper or lower lung involvement.

TERMINOLOGY

Abbreviations and Synonyms

Definitions

Proliferation of atypical smooth muscle cells in lungs and thoracic & retroperitoneal lymphatics

IMAGING FINDINGS

General Features

Best diagnostic clue
- Woman of childbearing age; progressive dyspnea
  - Radiography: Large volumes, reticular opacities, chylothorax, or spontaneous pneumothorax
  - CT: Diffuse bilateral thin-walled air-filled cysts with intervening normal lung
Patient position/location: Diffuse bilateral pulmonary involvement
Size: Variable cyst sizes ranging from 2-5 mm, but larger cysts ranging from 6-12 mm may also occur
Morphology: Spherical cysts with smooth thin walls

CT Findings

Lung
- Diffuse bilateral thin-walled cysts with normal intervening lung
  - Relative sparing of lung apices & lung bases
  - Visualization of lung cysts in patients with normal or near-normal radiographs
- Pulmonary involvement may be initially mild but becomes profuse & severe as disease progresses
- Variable cyst sizes, typically 2-5 mm, but larger cysts 6-10 mm & dominant cysts also observed
  - Typically smaller cysts in early disease and larger cysts in late disease
- Typically round cysts; ovoid & polygonal cysts; polygonal cysts more common in severe disease
- Cyst walls range from barely perceptible to 2-4 mm in thickness
Pleura
- Pleural effusion; chylothorax
  - Rarely exhibits fat attenuation
- Pneumothorax
- Hydropneumothorax
Other
- Lymphadenopathy; thoracic, abdominal, pelvic
- Renal angiomyolipomas in 20-54%

Radiographic Findings

Lung
- Normal or increased lung volumes
- Diffuse bilateral symmetric reticular opacities
- Radiographs may appear normal in spite of involvement with cystic disease
Pleura
- Pneumothorax in 39-53%
- Pleural effusion in 10-20%; unilateral or bilateral

Imaging Recommendations

Best imaging tool
- HRCT is more sensitive than radiography
- Extent of disease correlates with expiratory volumes and diffusion capacity
Protocol advice: Coronal reformations help confirm diffuse cephalocaudal pulmonary involvement
Screening recommendations
- Women with TSC: Once after age of 18
- Women with unexplained recurrent pneumothorax
- Women with little or no tobacco use who have diagnosis of primary spontaneous pneumothorax (or emphysema)

DIFFERENTIAL DIAGNOSIS

Langerhans Cell Histiocytosis

Centrilobular Emphysema

Smokers, occurs in both males and females
Upper lobe predominant involvement
Centrilobular lucencies with imperceptible walls; visualization of central lobular artery

Lymphocytic Interstitial Pneumonia (LIP)