Purpose or Case Report: Pleuropulmonary blastoma represents a rare, primary pulmonary malignancy with an incidence of 25-50 cases a year within the United States (Knight 2019). In children under 6 years of age, it is the most common primary pulmonary malignancy, comprising approximately 25% of cases (Dehner 2019). It is an autosomal-dominant condition associated with the DICER1-related tumor susceptibility syndrome. This syndrome includes other neoplastic etiologies such as Sertoli-Leydig tumors of the ovary and cystic nephroma. It is usually diagnosed in childhood, as early as months after birth, and can be subdivided into three types based on tumor composition: cystic, mixed cystic and solid, and solid. The disease is believed to start as a cystic lesion that progressively becomes more solid over time, with morbidity/mortality outcomes directly tied to time of diagnosis.

Our patient was a 2-month-old female, with a known family history of DICER1 mutation in the mother, who presented to the hospital for projectile vomiting. Abdominal ultrasound revealed ileocolic intussusception, which was confirmed to be secondary to an ileal hamartoma on surgical small bowel resection. Subsequent genetic testing confirmed the presence of DICER1 mutation. Follow up CT chest at 6-months-old showed a right lower lobe multi-septate 2.1 x 2.0 cm cystic lesion as well as an adjacent sub-centimeter cystic lesion suspicious for type 1 pleuropulmonary blastoma versus congenital pulmonary airway malformation (CPAM). A multi-disciplinary conference opted for right lower lobectomy given the risk of the lesion. Pathology confirmed type 1 pleuropulmonary blastoma. Subsequent retroperitoneal and pelvic ultrasounds were negative for renal or ovarian abnormality.

Pleuropulmonary blastoma is an exceedingly rare diagnosis that is easily overlooked or misdiagnosed as benign etiology such as CPAM. It is important to note that any pulmonary cystic lesion in a pediatric patient warrants interval follow-up for continued assessment of the lesion. If a pulmonary cystic lesion is identified, subsequent renal and pelvic imaging should be obtained to rule out other lesions that may co-exist as part of a genetic syndrome such as DICER1. Timely diagnosis is critical as it directly influences patient mortality/morbidity.
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