Pleuropulmonary blastoma: a report on 350 central pathology-confirmed pleuropulmonary blastoma cases by the International Pleuropulmonary Blastoma Registry.

BACKGROUND: Pleuropulmonary blastoma (PPB) has 3 subtypes on a tumor progression pathway ranging from type I (cystic) to type II (cystic/solid) and type III (completely solid). A germline mutation in DICER1 is the genetic cause in the majority of PPB cases.
METHODS: Patients confirmed to have PPB by central pathology review were included, and their clinical characteristics and outcomes were reported. Germline DICER1 mutations were sought with Sanger sequencing.
RESULTS: There were 435 cases, and a central review confirmed 350 cases to be PPB; 85 cases (20%) were another entity. Thirty-three percent of the 350 PPB cases were type I or type I regressed (type Ir), 35% were type II, and 32% were type III or type II/III. The median ages at diagnosis for type I, type II, and type III patients were 8, 35, and 41 months, respectively. The 5-year overall survival (OS) rate for type I/Ir patients was 91%; all deaths in this group were due to progression to type II or III. OS was significantly better for type II versus type III (P = .0061); the 5-year OS rates were 71% and 53%, respectively. Disease-free survival (DFS) was also significantly better for type II versus type III (P = .0002); the 5-year DFS rates were 59% and 37%, respectively. The PPB type was the strongest predictor of outcome. Metastatic disease at the diagnosis of types II and III was also an independent unfavorable prognostic factor. Sixty-six percent of the 97 patients tested had a heterozygous germline DICER1 mutation. In this subset, the DICER1 germline mutation status was not related to the outcome.
CONCLUSIONS: Cystic type I/Ir PPB has a better prognosis than type II, and type II has a better outcome than type III. Surveillance of DICER1 carriers may allow the earlier detection of cystic PPB before its progression to type II or III PPB and thereby improve outcomes.