are then unable to survive after removal of that support. In the few cases reported, an association with cardiovascular abnormalities and dermal hypoplasia has been noted. Grossly, the lungs are small, with a total weight of v50% of that expected based on gestational age. The lungs are firm and show a diffusely granular surface (fig. 2). Microscopically, the tissue consists entirely of bronchial-like structures with muscle, glands and numerous cartilage plates. More distal components, such as proximal bronchioles, are only rarely seen. The intervening tissue is prominent and consists of loose-to-dense mesenchymal cells and collagen, along with thick-walled arteries, large thin-walled vascular channels, collections of amorphic basophilic debris and foci of extramedullary haematopoiesis. CPAM type 1 CPAM type 1 is composed of medium and large cysts that appear to be primarily of bronchial and bronchiolar origin. It is the most frequently occurring type (60–70% of cases), and, although seen primarily in the first month of life, may also be first diagnosed in older children and, rarely, young adults [4]. Clinically, most patients present with increasing respiratory distress shortly after birth, but older patients may present with cough, fever or chest pain. The severity of symptoms in newborn children is related to the size of the lesion as a whole and to the size and expansion of individual cysts. The lesion may present in utero as a solid thoracic mass during the first trimester, but, in most instances, will collapse during the second or third trimester to allow normal growth of the uninvolved lobes of the lung. The lesion then re-expands after birth as the cysts fill with air. Radiographically, air-filled or air/fluid- filled cysts are apparent in one or more lobes, with compression of adjacent lung, flattening of the diaphragm and shift of the mediastinum. Grossly, cysts are usually limited to one lobe (95%), but are rarely multiple or bilateral (fig. 3). The present authors have seen one case in which all lobes were affected. The cysts Fig. 1. – Schematic drawing of tracheobronchial tree illustrating the possible site of origin of the five types (0–4) of congenital pulmonary airway malformation based on the histological features of each type. CLASSIFICATION OF CHILDHOOD CYSTIC LUNG LESIONS 5