The observation that PPB may occur in long-standing lung cysts raises difficult therapeutic issues. Many authors have addressed the management of pulmonary cysts and PPB [see Bibliography, Focuses: cyst, cyst management, and bilateral].
What is the period of risk for developing PPB in cysts? In 38 Registry and Bibliography cases, Types II and III PPB appeared weeks to 96 months (median 21 months) after a cyst was first observed (unpublished Registry compilation) (the 96-month interval was in a child whose cyst was noted at age 4 years. this case has been reviewed by the registry and reported by Hasiotou and by Dosios Bibliography). Some children with cysts had interval chest x-rays over many months, showing no change in the cysts, only to have extensive PPB develop months later. Even in children who had cysts removed, PPB may develop months later, indicating that observation must continue. The following data summarize the cyst course in these 38 children (unpublished Registry compilation):
|Age Cyst first noted||0 - 48 months (median age 18 months)|
|Duration of cyst observation||0.5 - 96 months (median interval 21 months)|
|Age PPB diagnosed||5 - 144 months (median age 36 months)|
A graph depicting the cyst-to-PPB time course in 21 of these 38 cases is presented here and in the Appendix/Data Resources. With regard to the time at which PPB may develop in cysts, the chronological age of the patient is more important than the duration of cyst observation. Note in the graph, that these children with cysts developed Types II and III PPB, suggesting that the observed cysts became or were "latent" Type I PPB during some of the observation period. These facts should guide surveillance decisions.
The Registry recommends that the threshold for excision of a cyst should be very low in the following high-risk children:
- in children with PPB
- in children with unilateral or bilateral lung cysts,
- who have other evidence of the constitutional/syndromic manifestations of PPB
- who have a family history of childhood cancer or the constitutional manifestations of PPB
Surveillance after removal of cysts or when cysts remain under observation should continue until the child is at least 5 years of age, based on the data noted above. (see Constitutional/Syndromic Disease and see Bibliography, Focuses: cyst, cyst management, familial/constitutional disease, and bilateral)