Pleuropulmonary blastoma type 1

Pleuropulmonary blastoma (PPB) type 1 is a rare malignant embryonal tumor of the lung that occurs almost exclusively in young children, typically presenting before the age of 2 years. It is the most common primary malignant lung tumor of childhood. PPB type 1, also known as the purely cystic form, is the earliest and least aggressive stage of pleuropulmonary blastoma. It presents as a multiloculated cystic lesion in the lung or pleura that can be mistaken for a congenital pulmonary airway malformation (CPAM) or other benign lung cysts on imaging. Symptoms may include respiratory distress, cough, pneumothorax, or recurrent pulmonary infections, though some cases are discovered incidentally on prenatal or postnatal imaging. PPB type 1 is strongly associated with germline pathogenic variants in the DICER1 gene, which plays a critical role in microRNA processing and gene regulation. This association places PPB type 1 within the DICER1 tumor predisposition syndrome, which carries an increased risk for other neoplasms including cystic nephroma, ovarian Sertoli-Leydig cell tumors, thyroid neoplasms, and other conditions. Family members may carry the same DICER1 variant and be at risk for related tumors, making genetic counseling and surveillance essential. The primary treatment for PPB type 1 is complete surgical resection of the cystic lesion. When completely excised, the prognosis for type 1 PPB is generally favorable, with reported survival rates exceeding 90%. However, if untreated or incompletely resected, type 1 PPB can progress to the more aggressive type 2 (cystic and solid) or type 3 (purely solid) forms, which carry significantly worse prognoses and typically require adjuvant chemotherapy. The role of adjuvant chemotherapy in type 1 PPB remains debated, though it may be considered in certain clinical scenarios. Long-term follow-up is recommended due to the risk of recurrence and the development of DICER1-associated tumors.

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