CPAM type 4 and PPB PPB is a rare primary pulmonary tumour in children, with y75 cases reported in the literature [19]. There is an equal sexual incidence and the vast majority occur during the first 4 yrs of life, although cases have been seen in older children and in an adult aged 36 yrs. Presenting symptoms include respiratory distress, nonproductive cough, fever, chest pain or a combination of symptoms of days’ to weeks’ duration [6]. Conditions associated with PPB are seen in nearly 25% of patients, and include a positive family history of childhood neoplasms, including PPBs, in siblings, cousins and other close relatives. Other associations in PPB patients include medulloblastoma, ovarian teratoma, Hodgkin’s lymphoma, leukaemia, thyroid dysplasia and neoplasia, malignant germ cell tumour and nephroblastic lesions. Imaging studies may show a solid (62%) or cystic (38%) lesion that may be Fig. 8. – Congenital pulmonary airway malformation type 4. a) The cysts are lined with cells with round nuclei and scant cytoplasm (haematoxylin and eosin stain). b) These lining cells are marked intensely with thyroid transcription factor (TTF), indicating that they are alveolar lining type 2 cells (TTF immunohistochemical stain). CLASSIFICATION OF CHILDHOOD CYSTIC LUNG LESIONS 13