Discussion
In the next half of my presentation, I will briefly talk about pleuropulmonary blastoma, specifically type I (PPB type I), and then describe a proposed approach to the workup and treatment of lung cyst.
Pleuropulmonary blastoma is a rare primary intrathoracic tumor of childhood. There are only about 300 cases that have been reported worldwide. It is divided into three types: type I is purely cystic in gross appearance; type II is cystic and solid; and type III is entirely solid. The origin of the tumor is unclear, and so far there are theories but none of them is as of yet proven: (1) the tumor is a malignant transformation of existing lung cysts, or (2) it is a collection malignant lesions in the form of lung cysts.
During infancy, the lesion clinically presents with mild to severe respiratory distress or pneumothorax. However, later on, , it is usually found as an incidental discovery on chest X-ray. After reviewing 50 cases, Priest1 and colleagues reported that the age of presentation is between 0 to 28 months. Sixty percent of cases present in the right chest, and bilateral presentation is rare2.
PPB type I may occur as2 isolated disease, Constitutional Disease, or PPB/Neoplasia Cancer Family Syndrome. In Constitutional Disease, the patient will have extrapulmonary dysplastic/neoplastic lesions, e.g.: cystic nephroma of the kidney, nodular thyroid dysplasias, Wilms tumor, or medulloblastoma 3. In PPB/Neoplasia Cancer Family Syndrome, there is frequent occurrence of extrapulmonary dysplasia/neoplasia (as mentioned above) in PPB children and their families. The latter type represents 25% of the cases2,3,4,5.
The diagnosis of PPB type I is difficult because there is no preoperative imaging that can reliably differentiate between congenital cystic lesions and PPB type I6. The role of fine needle aspiration in diagnosis has not been uniformly successful, and so far there is no available genetic testing for the tumor2. The acceptable method of diagnosis is removing the tumor en bloc and sending it for histopathology examination. The diagnosis needs a high-index of suspicion by the clinician in order to convey his concerns to the pathologist, and by the pathologist in order to make several and multiple cuts through the cyst lining, as the tumor cells are not uniformly spread through the cyst.
Priest7 and colleagues reported some helpful clinical features that may suggest the diagnosis of PPB type I. These included the presence of a lung cyst in a child younger than 5 years of age with multiple or bilateral lung cysts, renal cystic disease, or family history of childhood neoplasia/dysplasia. However, there are no clinical features to make the diagnosis less likely.
The treatment of PPB consists of early resection rather than observation, and total surgical resection (lobectomy) plus adjuvant chemotherapy decreases recurrence rate from 40% to 6%8.
The follow up protocol, suggested by the International PPB Registry2, indicates that each patient who was diagnosed for pleuropulmonary blastoma type I should have a monthly Chest radiograph and chest CT every 3 months during first 2 years after diagnosis, and then chest CT, only, every 3 months till age of 60 months. The Registry made a comment that although the amount of radiation from the CXR and CT scan is big, the risk of missing recurrent tumor, in a more aggressive form, is much bigger and would be devastative. The clinician, however, can use low-radiation CT scans. During the follow up period, new lesions should be removed immediately.
The prognosis2 for PPB type I is good, and the overall survival is 83%. Indolfi9 and colleagues reported that total resection is a good prognostic factor. There were no metastases that have been reported, and all recurrent cases were type II or III PPB, which are more progressive and aggressive forms.
Based on the above description, our patient’s data, and our previous experience, the approach to primary lung cysts at our institution was to ask for a chest CT scan with contrast, and then to remove the symptomatic and infected cysts. We also suggest the removal of suspicious primary cysts, even if they are asymptomatic, for diagnosis.
Next page / / References