[Prenatal presentation of pleuropulmonary blastoma associated to DICER1 syndrome: differential diagnosis of congenital pulmonary malformation].

Pleuropulmonary blastoma (PPB) is the most common pediatric malignant primary lung tumor. It's associated with the DICER1 gene pathogenic germline variants. Antenatal presentation is infrequent and poses a challenge in the differential diagnosis of congenital pulmonary airway malformation (CPAM).

Objective: to report a case of unusual presentation of PPB associated with DICER1 syndrome and to describe the difficulty in differentiating it from CPAM.

Clinical case: Male patient with prenatal diagnosis of hypervascular left lung lesion, with mediastinal shift and progressive growth, initially interpreted as CPAM. He was born at 38 weeks, requiring transitory treatment with positive pressure due to ventilatory impairment. A CT scan with contrast showed a large multilocular cystic mass containing air causing mass effect, requiring open left upper lobectomy. Histology results were compatible with type I PPB, with negative margins, and positive genetic study for DICER1 syndrome. Seven weeks post-resection, an aerial image was detected in the upper left side of the chest, with progressive growth, requiring a new tumor resection and upper segmentectomy, with biopsy corresponding to recurrence of type I PPB with negative margins. He received adjuvant treatment with chemotherapy, with follow-up for 2 years, remaining asymptomatic, without recurrence, and with negative screening for other neoplasms associated with DICER1 syndrome. Among the family history, the mother had papillary thyroid cancer and tested positive for the mutation.

Conclusion: PPB is a rare cancer, difficult to distinguish from CPAM, especially in its antenatal presentation. Nowing its association with DICER1 syndrome and performing a genetic study are key to the early detection of BPP and the search for other tumors associated with the syndrome.