Lung cysts and PPB

Lung cysts are common in individuals with DICER1 variation. Most lung cysts in individuals with DICER1 variation represent Type I or Ir PPB. Please see section on PPB for additional information. 

Lung cysts may present with shortness of breath due to large size or pneumothorax (leakage of air into the chest cavity outside of the lung). Lung cysts may also be asymptomatic and detected on imaging studies performed for another reason including routine surveillance imaging.

Chest x-ray or chest CT may show one or more cystic lesions which may be multiseptated. These may be near the pleura or deep within the parenchyma of the lung.

Two potential approaches are resection or observation. Whether to observe or perform surgery for removal depends on several factors including size and appearance as well as the age of the individuals and evidence of growth. Risk of progression from Type I to Type II or III PPB is more common in individuals under the age of 7 years. Most Type I PPBs likely do not progress but resection may substantially reduce this risk. If surgery is undertaken, an approach to avoid risk of rupture/spillage and optimize the likelihood of clear margins should be emphasized. Consultation with an experienced pediatric thoracic surgeon is advised.

Lung cysts are frequently noted in adults with pathogenic germline DICER1 variants and are assumed to be type Ir PPB. As the risk for malignancy is low, resection of these lesions in adults is not typically undertaken for oncologic indications but may be considered on the basis of size and location due to the potential risk of pneumothorax or superinfection.

Please see sections on Type I and Ir PPB.

Management at birth: Current guidelines suggest a chest xray (chest radiograph) at birth for all children at risk of a pathogenic germline DICER1 variant to screen for any large pulmonary cysts.

Current guidelines recommend genetic counseling with consideration of DICER1 molecular testing to be performed ideally between birth and three months of age. In children who are found to be carriers of a pathogenic germline DICER1 variant, health care providers and families should consider chest computed tomography (CT) scan prior to nine months of age, preferably between 3 and 6 months of age, as the incidence of Types II and III PPB increases after 1 year of age.

Because of the radiation dose and possible need for sedation with cross-sectional imaging, chest X-rays are the primary screening modality. In the absence of pulmonary cysts/PPB, most individuals with DICER1 mutations detected in early childhood will undergo only two chest CTs. If the first chest CT is normal with no evidence of cysts, a follow-up, low-dose chest CT at approximately 2.5 years of age, prior to the peak incidence of Types II and III PPB should be considered. In the absence of concerning radiographic findings, a chest X-ray every 6 months from birth through 8 years of age and then annually from 8 to 12 years of age is currently recommended. The utility of routine surveillance chest X-ray or CT in adolescence and adulthood is unknown; however, when DICER1 variation is detected after age 12, a baseline CXR or chest CT may be considered.

Currently, CT offers a higher level of sensitivity for the detection of cystic lung lesions not achievable with chest X-ray alone. When CT is performed, techniques to minimize radiation exposure should be included. As novel magnetic resonance imaging (MRI) techniques are developed that will eventually allow detection of small cystic lesions, transition to non-radiation containing cross-sectional imaging should be considered.

When a pulmonary cyst is identified in a young child with a pathogenic germline DICER1 variant or family history of a DICER1-related condition, it should be assumed to be Type I PPB until proven otherwise.