Pleuropulmonary blastoma type 3

Pleuropulmonary blastoma (PPB) type 3 is the most aggressive form of pleuropulmonary blastoma, a rare malignant embryonal tumor arising in the lung, pleura, or mediastinum. PPB is classified into three types reflecting a progression from cystic (type 1) to mixed cystic and solid (type 2) to purely solid (type 3). Type 3 PPB presents as a large, solid, high-grade sarcomatous mass within the chest that may compress or invade surrounding lung tissue, the pleura, the mediastinum, and the diaphragm. It predominantly affects young children, with most cases diagnosed between the ages of approximately 2 and 6 years. Key symptoms of PPB type 3 include respiratory distress, cough, chest pain, fever, and sometimes pneumothorax. Because the tumor can grow rapidly and is often large at diagnosis, patients may present with significant compromise of pulmonary function. Metastasis, particularly to the brain and central nervous system, can occur and represents a serious complication. PPB type 3 is strongly associated with germline loss-of-function pathogenic variants in the DICER1 gene, which encodes a key enzyme in microRNA processing. Families carrying DICER1 mutations may also be at risk for other conditions within the DICER1 tumor predisposition syndrome, including cystic nephroma, ovarian Sertoli-Leydig cell tumors, thyroid neoplasms, and other rare tumors. Treatment of PPB type 3 typically involves a multimodal approach combining aggressive surgical resection with intensive combination chemotherapy. Regimens often include agents used in pediatric sarcoma protocols, such as vincristine, actinomycin D, cyclophosphamide, ifosfamide, and doxorubicin. Despite treatment, the prognosis for type 3 PPB is significantly worse than for types 1 and 2, with a 5-year overall survival rate estimated at approximately 45-50%. Genetic counseling and surveillance of family members for DICER1-related conditions are important components of management. The International Pleuropulmonary Blastoma/DICER1 Registry coordinates research and clinical guidance for affected families.

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