Type I Pleuropulmonary Blastoma Originating from an Extralobar Sequestration

European Respiratory & Pulmonary Diseases, 2016;2(1):23–5 DOI: http://doi.org/10.17925/ERPD.2016.02.01.23

Abstract:

Pleuropulmonary blastomas (PPBs) represent a rare, malignant neoplasm in infants and children. Despite their overall rarity, they are the most common primary lung malignancy in young children. Typically originating as cystic lesions that are amenable to easy resection, PPBs can progress to solid masses prone to metastases if not identified and treated early enough. In their early cystic form, PPBs are often difficult to distinguish from congenital pulmonary airway malformations based on clinical and radiographic findings. We report on an eight-month-old girl who presented to our institution with a large, right-sided, cystic lung lesion, which had not been apparent on a chest radiograph shortly after birth. After excision of the lesion, pathology demonstrated it to be a type I PPB, which was unique for its apparent extra lobar origin. We review the relevant literature concerning PPBs, as well as the debate surrounding resection of cystic lung lesions in infants and children.
Keywords: Pleuropulmonary blastoma, cystic lung lesions, sequestration, pathology, malignancy
Disclosure: Scott Bickel, Bethany Carnes, Matthew Thompson, Sheldon Bond and Ronald Morton have nothing to disclose in relation to this paper. No funding was received in the publication of this article. No images contained within this manuscript have previously been published.
Compliance with ethics: All procedures were followed in accordance with the responsible committee on human experimentation and with the Helsinki Declaration of 1975 and subsequent revisions, and informed consent was received from the patient involved in this case study.
Received: February 23, 2016 Accepted March 30, 2016
Correspondence: Ronald Morton, Division of Pediatric Pulmonology, University of Louisville, 571 South Floyd St, Suite 414, Louisville, KY 40202, US. E: Ron.morton@louisville.edu
Open Access: This article is published under the Creative Commons Attribution Noncommercial License, which permits any non-commercial use, distribution, adaptation and reproduction provided the original author(s) and source are given appropriate credit.

Case report
An eight-month-old girl presents with mild, intermittent tachypnea of several months duration. The girl’s past medical history was unremarkable except for a short neonatal intensive care unit (NICU) course secondary to respiratory distress following a term, vaginal delivery. She was meeting growth and developmental milestones. A chest radiograph taken while in the NICU was unremarkable (see Figure 1A). The repeat chest radiograph and subsequent computed tomography (CT) with contrast performed at an outside institution revealed a large, right-sided, septated cystic lesion causing mediastinal compression (see Figures 1B, 1C and 1D). Despite the use of intravenous (IV) contrast, the origin of the blood supply for the mass was difficult to ascertain with certainty on the CT images.

She was sebsequently transferred to a tertiary children’s hospital (Kosair Children’s Hospital, Louisville, KY) where she underwent evaluation by the paediatric pulmonary service as well as by paediatric surgery. There was initial concern that perhaps an endobronchial lesion or other airway anomaly had formed the cyst through a ball-valve mechanism. A congenital pulmonary airway malformation (CPAM) was another consideration but felt to be less likely given her normal chest radiograph at birth. To help exclude an endobronchial lesion, flexible bronchoscopy was undertaken. This procedure, however, was unrevealing of a cause, demonstrating normal airway anatomy apart from evidence of external compression of the right mainstem bronchus. The patient then proceeded to undergo exploratory thoracotomy and resection of the mass. She was monitored post-operatively in the paediatric intensive care unit (PICU) and overall had an uneventful course. Post-resection imagery showed complete re-expansion of the right lung. The intermittent tachypnea was no longer present once she recovered from surgery.

Operatively, the mass was found to be mostly free from the lung with small attachments at the superior portion of the mass anteriorly, around the middle and upper lobe. The mass was not intralobar and a number of small vessels were present and ligated in the posterior gutter and elsewhere. It was felt intraoperatively that the blood supply was entirely systemic as no pulmonary circulation could be identified. The mass was also noted to be grossly devoid of bronchial components and speculated to be air filled via accessory connections to the lung.

Grossly, the mass was brown-red and fully encapsulated by a shiny smooth pleural surface measuring 7 x 7 x 1.5 cm. The mass did not share a vascular supply with the lung, making it extralobar, which is unusual for a PPB. Sectioning showed multiple areas of dilated and tortuousappearing tissue grossly consistent with dilated vessels or cysts with haemorrhage. Microscopic examination showed a multicystic lesion arising in a background of normal lung with bronchioles. The cysts exhibited a very cellular and primitive cyst wall that formed a cambiantype layer in areas with an unremarkable cuboidal cell lining (see Figure 2A and B). There were areas in the lung tissue that showed mature rhabdoid- type cells with abundant eosinophilic cytoplasm (see Figure 2C and D). There were occasional nodules of the immature spindled cells present in the cyst wall but no diffusely solid areas. The immature stroma showed strong cytoplasmic staining for desmin and smooth muscle actin and patchy nuclear staining for myogenin (see Figure 2E and F). The cuboidal lining cells were positive for Pankeratin AE1/ AE3 (see Figure 2G). The areas of rhabdoid-type cells showed diffuse strong cytoplasmic staining with desmin (see Figure 2H). PHH3 staining showed greater than 20 mitoses per 10 high power fields (not shown). These findings are all features of a type I pleuropulmonary blastoma (PPB), apparently arising from an extralobar sequestration. Only one other case of a PPB associated with an extralobar sequestration was identified during our literature search.1

Our patient was followed closely by our oncology colleagues who performed an abdominal and pelvic CT to evaluate for other lesions or masses, such as cystic nephromas, which was negative. The family was counselled on multiple occasions about the utility of DICER1 mutation analysis, however they did not agree to testing while being followed at our centre. The child had no other siblings and there was a strong family history of tumours with lung and colon cancer on the paternal side and throat and lung cancer on the maternal side. It is unclear if any of these tumours may also be linked to DICER1 mutations.

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Keywords: Pleuropulmonary blastoma, cystic lung lesions, sequestration, pathology, malignancy