Pleuropulmonary blastoma in an adult

Introduction: Pleuropulmonary blastoma (PPB) is a dysontogenetic neoplasm of childhood categorized with other embryonal tumors that include Wilms' tumor, hepatoblastoma, neuroblastoma and embryonal rhabdomyosarcoma. PPB typically presents in young children as pulmonary and/or pleural-based masses which are cystic, solid, or both cystic and solid. Histologically, PPB is identified by a primitive blastema and sarcomatous elements in the absence of an epithelial component as in the classic pulmonary blastoma (PB) which typically presents in adults. The case reported here is the first of PPB presenting in an adult. Case Presentation: A previously healthy 36-year-old white male presented to an outside hospital in July 1997 with severe exertional dyspnea, progressive over several weeks in the absence of chest pain, cough, fever, or weight loss. Physical examination was remarkable for absent breath sounds in the left hemithorax. Chest roentogram (CXR) showed an apparent large left pleural effusion. Computed tomography (CT) of chest revealed a multilocular cystic mass. Clinical impression was empyema and thoracentesis removed one liter of exudate. Bacterial cultures were negative and cytology non-diagnostic. Left anterior thoracotomy exposed a large cystic and solid mass with apparent origin in the infracardiac mediastinum that displaced the left lung into the apex of the chest and flattened the diaphragm. The initial pathological diagnosis was a "primitive sarcoma" which was later amended to PPB with cystic and solid features (type II PPB). Post-operative chemotherapy was delayed by patient relocation. Six weeks post-thoracotomy, the patient presented to our hospital in respiratory distress with severe chest pain in the absence of cough, hemoptysis, fever, or weight loss. Breath sounds were absent on the left and CXR showed opacification of left hemithorax with right mediastinal displacement. Laboratory evaluation showed leukocytosis 14,800/cumm, serum urate of 16 mg/dL, and mild elevation of liver enzymes. Chest CT revealed a large hypodense mass occupying the left hemithorax and compressing the upper abdomen. Within a day of admission, the patient developed respiratory failure requiring mechanical ventilation. A chest tube drained three liters of exudative effusion with non-diagnostic cytology. Chemotherapy with doxorubicin and ifosfamide was initiated and complicated by neutropenic sepsis. After three weeks of intensive support the respiratory function improved allowing ventilator weaning. He continued to improve symptomatically and resumed daily function without supplemental oxygen. Chemotherapy was continued using a modified pediatric rhabdomyosarcoma regimen of alternating courses of cyclophosphamide, doxorubicin, vincristine and ifosfamide, etoposide, and vincristine, with G-CSF support. Follow-up chest CT at six and twelve week intervals showed marked decrease in the size of the mass. After six cycles a plateau in response was reached and surgical removal of residual tumor was discussed. Unfortunately, the patient developed right-sided hip pain and magnetic resonance imaging showed a five by seven centimeter lesion in the right iliac bone, biopsy proven as metastasis. The patient is receiving radiation therapy with plans for second-line chemotherapy upon completion. His past medical history is remarkable only for epistaxis during childhood and fever of unclear etiology at age five. His father had colon cancer and his mother had diabetes mellitus. There is no family history of childhood neoplasms or affected siblings. Discussion: This patient was a previously healthy adult presenting with dyspnea and a large cystic mass. The differential diagnosis included loculated empyema, necrotizing pneumonia, and primary or metastatic neoplasia. At surgery it became apparent that this was a pleural-based tumor composed of soft, glistening solid areas and multiple thin walled cysts filled with serous fluid. Microscopically, the cystic areas were lined with respiratory-type epithelium, beneath which was a population of primitive small cells with a myogenic immune phenotype. The solid areas of the tumor were composed of immature blastema and high grade pleomorphic sarcoma. The iliac metastasis contained the blastemal component. Conclusions: All cases of PPB have occurred in children whose ages have ranged from neonate to 12 years old with an average age of 38.6 months by report in a recent comprehensive series. The patient is the first adult to our knowledge to present with this rare dysontogenetic neoplasm which is a distinct clinicopathologic entity from classic pulmonary blastoma.