Sauropus androgynus-constrictive obliterative bronchitis/bronchiolitis - histopathological study of pneumonectomy and biopsy specimens with emphasis on the inflammatory process and disease progression

Aims: The histopathology of the Sauropus androgynus (SA)-constrictive bronc hiolitis obliterans (BO) is still controversial. A recent report using pneu monectomy specimens showed that the major histopathology was obliterative a rteriopathy with segmental necrosis of small bronchi instead of constrictiv e BO as previously described. Methods and results: We analysed semiquantitatively and immunohistochemical ly the histopathology of one pneumonectomy and four biopsies specimens of S A-associated lung disease. We found a significant number of constrictive an d obliterative bronchioles 1 mm or less in diameter and segmental inflammat ory destruction with complete luminal obliteration of the bronchi less than 3 mm in diameter in the pneumonectomy specimen (37% and 25%, respectively) . Fibromuscular intimal sclerosis of the bronchial arteries was identified in 15% of the bronchi 4 mm or less in diameter. The inflammation in these a irways was composed predominantly of T-lymphocytes, macrophages, mast cells and eosinophils. They were present throughout the evolutionary stages of t he bronchiolitis ranging from early oedematous to the late fibrotic obliter ative stage. Double immunohistochemical stains revealed negative proliferat ive cell nuclear antigen for most of the T-lymphocytes and macrophages but positive for fibroblasts. Conclusions: A more accurate histopathological designation of the SA-associ ated lung disease should be constrictive obliterative bronchitis/bronchioli tis, with the participation of T-lymphocytes, macrophages, mast cells, eosi nophils and fibroblasts in its morphogenesis. The persistent accumulation o f inflammatory cells was mediated predominantly by continued recruitment to the site of injury from the bloodstream, resulting eventually in the irrev ersible fibrosis of the bronchioles and the bronchi less than 3 mm in diame ter. Obliterative arteriopathy is suspected of being only an indirect contr ibuting factor.