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In a fetopathologic evaluation of 18 cases with amniotic bands, we discerned 3 types of lesions: (1) constrictive tissue bands, (2) amniotic adhesions, and (3) more complex anomaly patterns, designated as limb-body wall complex (LBWC). Constrictive bands are caused by primary amnion rupture with subsequent entanglement of fetal parts (mostly limbs) by shriveled amniotic strands. Adhesive bands are the result of a broad fusion between disrupted fetal parts (mostly cephalic) and an intact amniotic membrane. Most of the craniofacial defects (encephaloceles and/or facial clefts) occurring in these fetuses are not caused by constrictive amniotic bands, but are the result of a vascular disruption sequence with or without cephalo-amniotic adhesion. Our observations confirm the fact that amnion rupture is not a conditio sine qua non for the development of LBWC. However, LBWC is often complicated by rupture of the unsupported amnion with ensuing formation of constrictive bands. We think that the concept that considers the 3 lesions in question as a single pathogenetic entity is erroneous and will inevitably lead to a never-ending debate between followers of the 2 prevailing theories. In our view, the theories of Streeter and Torpin are not mutually exclusive but rather apply to different types of lesions. The recognition of constrictive amniotic bands, amniotic adhesions, and LBWC as discrete but often combined disruption sequences with important pathogenetic overlap may resolve many dilemmas in interpretation when a fetus exhibits classical constrictive bands beside more severe defects.

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Congenital cystic adenomatoid malformation is a rare developmental abnormality of the lung. In most earlier reported cases, the anatomy of the bronchial tree was poorly documented. We describe four cases studied following autopsy. Post-mortem bronchography or serial microscopical examination showed segmental bronchial absence or atresia in each of them. Our observations provide further evidence pointing to bronchial atresia as being the primary defect leading to the development of congenital cystic adenomatoid malformation. The morphology of the lesion, i.e. the type of malformation, is determined by the extent of dysplastic lung growth beyond the atretic segment. The aetiology of the bronchial atresia is probably heterogeneous and may either represent a primary malformation, or be the result of vascular disruption.

We report on 7 perinatal autopsy cases of primary congenital pulmonary lymphangiectasis (CPL) with bilateral chylothorax. This study demonstrates that primary CPL is often complicated by chylous pleural effusions with ensuing pulmonary hypoplasia. Conversely, CPL appears to be a constant pathological finding in spontaneous congenital chylothorax. These observations indicate a common pathogenesis for both disorders. The basic defect is not an intrinsic lung abnormality, but a developmental error of the lymphatic system resulting in a pulmonary lymphatic obstruction sequence. The cause of CPL is heterogeneous. Apparently, most cases are sporadic occurrences. We report the second instance of CPL in sibs. This indicates that some cases are genetically determined with autosomal recessive inheritance. CPL may also be part of a multiple congenital anomalies (MCA) syndrome such as Noonan, Ullrich-Turner, and Down syndrome.

The pulmonary neuroendocrine system consists of specialized airway endocrine epithelial cells, associated with nerve fibres. The epithelial cells, the pulmonary neuroendocrine cells (PNEC), can be solitary or clustered to form neuroepithelial bodies (NEB). During the last thirty years, the pulmonary neuroendocrine system has been intensively investigated and much knowledge of its function has been obtained. This text reviews work which dates from the last ten years. In this period, the picture of the pulmonary neuroendocrine system we previously had, has not fundamentally changed. The pulmonary neuroendocrine system is still regarded as an oxygen sensitive chemoreceptor with local and reflex-mediated regulatory functions, and as a regulator of airway growth and development. Continuing research has much more refined this picture. This text reviews several aspects of the pulmonary neuroendocrine system: phylogeny, the amine and peptide content of its epithelial cells, ontogeny and influence on lung development, the influence of hypoxia and nonhypoxic stimuli, immunomodulatory function, innervation and pathology. Among the discoveries of the past decade, three stand out prominently because of their great significance: additional proof that the neural component of the pulmonary neuroendocrine system is sensory, sound experimental evidence that PNEC stimulate airway epithelial cell differentiation and the discovery of a specific membrane oxygen receptor in the PNEC.

Partitioning of pulmonary resistance of 15 excised human and 5 canine lungs by means of a retrograde catheter demonstrated that the share of peripheral airways (with an ID of 2.4 mm or less) and of lung tissue in pulmonary resistance was markedly larger (44-96%) in humans than in dogs (41-59%). Similar percentages were found in patients with chronic obstructive pulmonary disease (COPD). The variations of resistance with volume during deflation and inflation of the lungs were due primarily to variations of peripheral resistance (Rp). The latter systematically increased at high and low lung volumes. Higher Rp values, with a more pronounced frequency dependence, were met in patients with COPD. A morphometrical study showed an inverse relationship between the value of Rp and the mean diameter of the terminal bronchioles, provided the airways density was taken into account.

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