Pleuropulmonary blastoma is a rare and highly aggressive pulmonary malignancy that can present as a pulmonary or pleural mass. In most cases, pleuropulmonary blastoma is associated with germline mutations of the DICER1 gene. The International Pleuropulmonary Blastoma Registry is a valuable resource for information on this rare malignancy.  
The following three subtypes of pleuropulmonary blastoma have been identified:
Histologically, these tumors appear as a multilocular cyst with variable numbers of primitive mesenchymal cells beneath a benign epithelial surface, with skeletal differentiation in one-half of the cases.  This form of disease can be clinically and pathologically deceptive because of its resemblance to some developmental lung cysts.
In the Pleuropulmonary Blastoma Registry experience, most Type I and Ir cysts are unilateral (74%), half are unifocal, and 55% are larger than 5 cm. Pneumothorax may be present at diagnosis in up to 30% of Type I and Ir pleuropulmonary blastoma cases. 
Anaplasia is present in up to 60% of the cases.  In the Pleuropulmonary Blastoma Registry, the median age at diagnosis was 35 months, and distant metastases were present at the time of diagnosis in 7% of cases. 
Median age at diagnosis in the Pleuropulmonary Blastoma Registry was 41 months, and distant metastases were present in 10% of patients at the time of diagnosis. 
|Type I||Type Ir||Type II||Type II/III or III|
|aAdapted from Messinger et al. |
|Relative proportion of pleuropulmonary blastoma cases||33%||35%||32%|
|Presence of germline DICER1 mutation||62%||63%||75%|
|Median age at diagnosis (months)||8||47||35||41|
|5-year overall survival||89%||100%||71%||53%|
In a comprehensive analysis of 350 patients reported by the Pleuropulmonary Blastoma Registry, only two prognostic factors were identified: the type of pleuropulmonary blastoma and the presence of metastatic disease at diagnosis.  (Refer to Table 1.) In three additional small cohort series, the ability to perform a complete surgical resection was also identified as a prognostic factor.   
The presence of a germline DICER1 mutation is not a prognostic factor. 
Close to two-thirds of patients with pleuropulmonary blastoma have a germline DICER1 mutation. Approximately one-third of families of children with pleuropulmonary blastoma manifest a number of dysplastic and/or neoplastic conditions comprising the DICER1 syndrome.    Most mutation carriers are unaffected, indicating that tumor risk is modest. 
The penetrance of DICER1 mutations associated with each pathologic condition is not well understood, but lung cysts, pleuropulmonary blastoma, and thyroid nodules are the most commonly reported manifestations in individuals who have loss-of-function mutations.  Most associated conditions occur in children younger than 10 years, although ovarian tumors and multinodular goiters are described in children and adults aged up to 30 years.   Surveillance and screening recommendations have been proposed. 
As with other cancer predisposition conditions, before individuals with DICER1 mutations are screened, factors that must be considered include typical age of onset of each disease, potential benefits of early detection, and risks and availability of screening modalities. A consensus panel convened by the International Pleuropulmonary Blastoma Registry has proposed guidelines for surveillance. In addition to imaging-based surveillance, individuals and families can be counseled at each visit regarding potential signs and symptoms of DICER1-associated conditions and undergo appropriate age-specific and gender-specific preventive screening studies (refer to Figure 1). 
Figure 1. Suggested signs and symptoms and imaging surveillance by system for individuals with DICER1 pathogenic variants. Adapted from Clinical Cancer Research, Copyright 2018, Volume 20/Issue 10, Pages 2251–2261, Kris Ann P. Schultz, Gretchen M. Williams, Junne Kamihara, et al.: DICER1 and Associated Conditions: Identification of At-risk Individuals and Recommended Surveillance Strategies, with permission from AACR.
Presenting symptoms are not specific, and commonly include the following:
The tumor is usually located in the lung periphery, but it may be extrapulmonary with involvement of the heart/great vessels, mediastinum, diaphragm, and/or pleura.   Tumor embolism is a known risk, and radiographic evaluation of the central circulation is performed to identify potentially fatal embolic complications. 
There are no standard treatment options. Current treatment regimens for these rare tumors have been informed by consensus opinion.
Treatment options for childhood pleuropulmonary blastoma include the following:
A complete surgical resection is required for cure. 
Data from the International Pleuropulmonary Blastoma Registry and the European Cooperative Study Group in Pediatric Rare Tumors (EXPeRT) suggest that adjuvant chemotherapy may reduce the risk of recurrence.  ;  [Level of evidence: 3iiiA] Responses to chemotherapy have been reported with agents similar to those used for the treatment of rhabdomyosarcoma.   
Information about National Cancer Institute (NCI)–supported clinical trials can be found on the NCI website. For information about clinical trials sponsored by other organizations, refer to the ClinicalTrials.gov website.
The following is an example of a national and/or institutional clinical trial that is currently being conducted:
Tumor tissue from progressive or recurrent disease must be available for molecular characterization. Patients with tumors that have molecular variants addressed by treatment arms included in the trial will be offered treatment on Pediatric MATCH. Additional information can be obtained on the NCI website and ClinicalTrials.gov website.
Cancer in children and adolescents is rare, although the overall incidence of childhood cancer has been slowly increasing since 1975.  Referral to medical centers with multidisciplinary teams of cancer specialists experienced in treating cancers that occur in childhood and adolescence should be considered for children and adolescents with cancer. This multidisciplinary team approach incorporates the skills of the following health care professionals and others to ensure that children receive treatment, supportive care, and rehabilitation that will achieve optimal survival and quality of life:
(Refer to the PDQ Supportive and Palliative Care summaries for specific information about supportive care for children and adolescents with cancer.)
Guidelines for pediatric cancer centers and their role in the treatment of pediatric patients with cancer have been outlined by the American Academy of Pediatrics.  At these pediatric cancer centers, clinical trials are available for most types of cancer that occur in children and adolescents, and the opportunity to participate in these trials is offered to most patients and their families. Clinical trials for children and adolescents diagnosed with cancer are generally designed to compare potentially better therapy with therapy that is currently accepted as standard. Most of the progress made in identifying curative therapy for childhood cancers has been achieved through clinical trials. Information about ongoing clinical trials is available from the NCI website.
Dramatic improvements in survival have been achieved for children and adolescents with cancer. Between 1975 and 2010, childhood cancer mortality decreased by more than 50%.  Childhood and adolescent cancer survivors require close monitoring because cancer therapy side effects may persist or develop months or years after treatment. (Refer to the PDQ summary on Late Effects of Treatment for Childhood Cancer for specific information about the incidence, type, and monitoring of late effects in childhood and adolescent cancer survivors.)
Childhood cancer is a rare disease, with about 15,000 cases diagnosed annually in the United States in individuals younger than 20 years.  The U.S. Rare Diseases Act of 2002 defines a rare disease as one that affects populations smaller than 200,000 persons. Therefore, all pediatric cancers are considered rare.
The designation of a rare tumor is not uniform among pediatric and adult groups. Adult rare cancers are defined as those with an annual incidence of fewer than six cases per 100,000 people, and they are estimated to account for up to 24% of all cancers diagnosed in the European Union and about 20% of all cancers diagnosed in the United States.   Also, the designation of a pediatric rare tumor is not uniform among international groups, as follows:
Most cancers within subgroup XI are either melanomas or thyroid cancer, with the remaining subgroup XI cancer types accounting for only 1.3% of cancers in children aged 0 to 14 years and 5.3% of cancers in adolescents aged 15 to 19 years.
These rare cancers are extremely challenging to study because of the low incidence of patients with any individual diagnosis, the predominance of rare cancers in the adolescent population, and the lack of clinical trials for adolescents with rare cancers.
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This PDQ cancer information summary for health professionals provides comprehensive, peer-reviewed, evidence-based information about the treatment of childhood pleuropulmonary blastoma. It is intended as a resource to inform and assist clinicians who care for cancer patients. It does not provide formal guidelines or recommendations for making health care decisions.
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PDQ® Pediatric Treatment Editorial Board. PDQ Childhood Pleuropulmonary Blastoma Treatment. Bethesda, MD: National Cancer Institute. Updated <MM/DD/YYYY>. Available at: https://www.cancer.gov/types/lung/hp/child-pleuropulmonary-blastoma-treatment-pdq. Accessed <MM/DD/YYYY>.
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