Pleuropulmonary blastoma - cystic nephroma: DICER1 syndrome

Clinical History

Female patient, 8 months old, with past history of bronchiolitis at 3 months of age. Delivery at full term, birth weight normal. As the anomaly persisted on chest X-ray at 13 months of age, chest CT was performed.

Imaging Findings

Fig. 1: Apical right pneumothorax, collapsed upper right lobe.
Fig. 2a-c : Large thin-walled cyst, without connection to bronchopulmonary tract. Collapsed URL. Bronchopulmonary dysplasia clinically unlikely. Not typical of lobar emphysema or bronchic atresia either.
Most likely radiological diagnosis: congenital pulmonary airway malformation, type 4

After surgical resection of the mass, and pathology examination the conclusion was: pleuropulmonary blastoma type I. DICER 1 heterozygous mutation was confirmed.

Upon follow up at 22 months of age, the radiological examination showed:
Fig. 3a: hypodense lesion in left kidney, with mild rim enhancement at portal phase
Fig. 3b: US showed ill-defined intraparenchymal lesion with hypoechogenic content, hyperechogenic rim, and internal septa.
Fig. 3c: MRI showed bright hyperT2 cystic lesion, thin wall, internal septa, no fat component, and once again mild enhancement of the cyst wall at portal phase.
No other suspicious lesion was found in CNS, thorax and abdomen.
Pathological result: cystic nephroma.
DICER1 syndrome.

Discussion

*The differential diagnosis of a cystic lung lesion in an infant includes congenital pulmonary airway malformation (CPAM), congenital lobar emphysema, intrapulmonary bronchogenic cyst, pneumatocele, and cystic or type I pleuropulmonary blastoma (PPB).
In 2001, Stocker expanded the classification of CPAM adding type 0 lesion (previously reported as acinar dysplasia of the lung) and type 4 lesion (a type of peripheral lung cyst manifesting with pneumothorax). Type 4 lesions comprise 10 to 15 percent of CPAMs. The cysts have a maximum diameter of 7 cm and consist of nonciliated, flattened, alveolar lining cells, with no mucus cells or skeletal muscles. Type 4 CPAMs may present at birth or in childhood, often with tension pneumothorax or infection, but they may also be identified as incidental findings in asymptomatic patients. Importantly, this type of CPAM is strongly associated with malignancy, especially with pleuropulmonary blastoma (PPB). [1]

*The primary differential diagnosis of a renal cyst in an infant includes cystic renal
dysplasia, polycystic kidney disease, cystic Wilms tumour, and cystic nephroma (CN).

*The combination of multicystic lesions in the lung and kidney in an infant is a common association for DICER1 spectrum associated tumours. [2] Germline mutations in DICER1 are associated with pleuropulmonary blastoma (PPB), cystic nephroma, nasal chondromesenchymal hamartoma, ovarian Sertoli-Leydig cell tumours, botryoid embryonal rhabdomyosarcoma of the uterine cervix, ciliary body medulloepithelioma, pineoblastoma, pituitary blastoma and nodular thyroid hyperplasia or thyroid carcinoma. These tumours may be seen in isolation or in constellation with other characteristic tumour types in individuals or family members.

*Clinical history is most of the time unable to indicate the right diagnosis, as most patients are either asymptomatic, or present with dyspnoea, cough, and/or fever.
*Imaging will detect a cystic lung lesion and/or cystic kidney lesion. However, imaging cannot differentiate benign causes from malignant causes, although some criteria may help [3].
*There are no internationally approved guidelines for treatment and surveillance.
*Surgical treatment of an asymptomatic congenital pulmonary airway malformation and other benign cause is controversial. However, neadjuvant chemotherapy in case of PPB is of possible relevant interest. [4]
*Because there is a risk of recurrence after treatment (surgery-only and surgery + chemotherapy), radiologists are asked to follow-up the patient with CT and abdominal US at least for 36 months after diagnosis [4].

*Take home message: Pitfall (child cystic lung lesion): Imaging cannot differentiate CPAM type 4 from PPB type 1.
If PPB is a possibility, radiologist should proceed to abdominal US and brain MRI, looking for DICER1-associated tumours.

Differential Diagnosis List

Final Diagnosis

DICER1 syndrome: Pleuropulmonary blastoma type I + cystic nephroma

URL:	https://www.eurorad.org/case/12442
DOI:	10.1594/EURORAD/CASE.12442
ISSN:	1563-4086