Pleuropulmonary Blastoma: Causes, Symptoms, Diagnosis and Treatment — Overview, Diagnosis & Treatment Options | MyMedicPlus

Pleuropulmonary blastoma (PPB) is a rare and highly malignant primary intrathoracic tumor of early childhood arising from primitive pulmonary mesenchymal cells, with most cases diagnosed between birth and 6 years of age (median age 2-4 years). It is the most common primary malignant lung tumor in children — in marked contrast to adults, where primary lung tumors are rare. PPB arises within the lung parenchyma, pleura, or both. The International Pleuropulmonary Blastoma Registry classifies PPB into three types based on gross pathology: Type I (purely cystic, typically presenting in infants under 2 years), Type II (mixed cystic and solid, typically ages 2-3 years), and Type III (purely solid, most aggressive, typically over age 3). DICER1 germline mutations underlie approximately 70% of cases, making PPB the hallmark neoplasm of DICER1 syndrome. Registry enrollment (International PPB/DICER1 Registry, Minnesota) is recommended for all newly diagnosed cases to provide diagnostic guidance, treatment support, and advance research.

DICER1 germline mutations are the dominant genetic cause of PPB, identified in approximately 70% of cases. DICER1 encodes an essential cytoplasmic RNA endoribonuclease that processes precursor microRNAs (pre-miRNAs) into mature miRNAs that regulate gene expression. Loss-of-function germline DICER1 mutations predispose to a spectrum of tumors across childhood and adulthood known collectively as DICER1 syndrome or DICER1 tumor predisposition. In PPB, a second somatic 'hit' in the DICER1 RNase IIIb domain (hotspot mutations at positions R944, E1705, D1709, and others) impairs miRNA processing, leading to dysregulation of developmental gene expression and malignant transformation of primitive mesenchymal cells. Type I PPB (purely cystic) may represent the earliest detectable manifestation of DICER1 syndrome, with incomplete somatic second-hit acquisition. Family members of PPB patients should receive DICER1 germline testing, as siblings, parents, and extended family members may be undiagnosed mutation carriers at risk for other DICER1-associated tumors.

The clinical presentation of PPB reflects its intrathoracic location and histological type. Respiratory symptoms dominate: progressive dyspnea, cough, and tachypnea from the primary intrathoracic mass or pleural disease are the most common presenting features in Type II and III PPB. Spontaneous pneumothorax (collapse of the lung from rupture of a cystic wall) is a classic and highly characteristic presentation of Type I PPB — any infant or young child presenting with spontaneous pneumothorax should be evaluated for PPB, as this is a diagnostic clue. Fever, chest pain, and decreased exercise tolerance occur with more advanced disease. Systemic constitutional symptoms including weight loss, fatigue, and poor feeding are common in Type II and III PPB. Brain metastasis — occurring most commonly to the cerebellum — is a feared complication of Type III PPB and may produce headache, ataxia, or focal neurological deficits at initial presentation or during follow-up. Some Type I PPB cases are identified incidentally on chest X-ray or CT performed for an unrelated respiratory illness.

CT of the chest with intravenous contrast is the primary imaging modality, characterizing tumor morphology (cystic, mixed, or solid), extent of pleural involvement, and mediastinal displacement. The imaging appearance of the three PPB types differs markedly: Type I appears as a pure cystic lung lesion (often resembling congenital pulmonary airway malformation, CPAM); Type II shows a mixed cystic and solid mass; Type III presents as a large heterogeneous solid mass. Surgical excision or image-guided core biopsy provides histological diagnosis; histopathology reveals the characteristic biphasic blastematous and mesenchymal elements. DICER1 mutation testing from tumor tissue (somatic hotspot mutations in the RNase IIIb domain) and from peripheral blood (germline mutations) should be performed for all cases. MRI of the brain is mandatory for Type II and III PPB to exclude cerebral metastases. Enrollment in the International PPB/DICER1 Registry is strongly encouraged for central pathology review and treatment guidance.

Type I PPB treatment is primarily surgical: complete surgical resection via lobectomy or pneumonectomy (if necessary) is curative when performed before progression to Type II or III. The role of adjuvant chemotherapy for Type I PPB remains debated, with Registry guidance suggesting chemotherapy (typically VAC: vincristine, actinomycin D, cyclophosphamide) for incompletely resected or histologically concerning Type I tumors. Type II and III PPB require multiagent chemotherapy combined with surgery. The standard chemotherapy backbone alternates VAC cycles with IE cycles (ifosfamide plus etoposide), following protocols adapted from soft tissue sarcoma and Ewing sarcoma regimens. Surgical resection of the primary tumor is performed after initial chemotherapy cycles when the tumor has responded and is deemed resectable. Radiotherapy is used for residual or incompletely resected disease and in the setting of brain metastasis. High-dose chemotherapy with autologous stem cell rescue is used in some centers for high-risk or relapsed Type III PPB. Treatment at a pediatric oncology center with thoracic surgical expertise is strongly recommended.

Primary prevention is not possible for PPB, but genetic identification of DICER1 mutation carriers enables presymptomatic surveillance that can detect PPB before it progresses from the treatable Type I to the more aggressive Type II or III. All first-degree relatives of a patient with PPB should receive genetic counseling and, if willing, germline DICER1 testing. Confirmed DICER1 mutation carriers in children should enter a structured surveillance program: chest MRI every 6 months from birth or mutation detection until age 8-10, then annually; renal and pelvic ultrasound annually from birth to detect cystic nephroma and other renal pathology; thyroid palpation and ultrasound annually; and age-appropriate surveillance for other DICER1-associated tumors throughout childhood and adolescence. Type I PPB lesions — which may initially appear as CPAM on imaging — should be resected rather than observed, as this can prevent malignant progression. All cases of CPAM-like lesions in children with DICER1 syndrome require pathological examination.

Parents should seek urgent pediatric or emergency evaluation for any young child (under 6 years) who develops sudden onset of respiratory distress, rapid breathing, or oxygen requirement — particularly if pneumothorax is identified on chest X-ray. Spontaneous pneumothorax in an infant or young child without antecedent trauma is not normal and should immediately trigger investigation for PPB. A persistent cough, respiratory infection that fails to resolve after appropriate antibiotics, or an incidentally discovered cystic or solid lung mass on chest imaging in a young child requires evaluation by a pediatric pulmonologist or thoracic surgeon with experience in pediatric malignancies. Any known DICER1 germline mutation carrier who develops respiratory symptoms or a new pulmonary finding on surveillance imaging should be assessed by a pediatric oncologist promptly. Families with a child diagnosed with PPB should be counseled that all siblings and parents should undergo genetic testing for DICER1 mutations.

Type I PPB: 5-year survival approximately 91% with complete resection. Type II: approximately 71%. Type III: approximately 53%. Metastatic disease (particularly brain metastasis) carries worse prognosis. DICER1 germline carriers require lifelong surveillance for PPB recurrence and second tumors in the kidney, thyroid, ovary, and other sites. The prognosis for Pleuropulmonary Blastoma: Causes, Symptoms, Diagnosis and Treatment varies depending on severity at diagnosis, the patient's overall health, and how promptly treatment is initiated. With early diagnosis and appropriate management, many patients achieve good outcomes and maintain quality of life. Regular follow-up with healthcare providers is essential to monitor progress, adjust treatment as needed, and detect any complications early. Adherence to prescribed treatments and lifestyle modifications significantly improves long-term prognosis.