LECTIN HISTOCHEMISTRY OF CHOLESTEROL CLEFT GRANULOMAS IN NON-SPECIFIC INTERSTITIAL PNEUMONIA (NSIP)

Background: Cholesterol cleft granulomas with clusters of giant cells were noted to be a common feature of non-specific interstitial pneumonia (NSIP). Objective: This study aimed to define the cell populations involved in the granulomas. Methods: The granulomas of 16 patients with cryptogenic fibrosing alveolitis (five cases with the histological features of NSIP, five with those of UIP and six cases of respiratory bronchiolitis) were examined histologically and by the use of immuno- and lectin histochemical markers. Results: Granulomas were discrete, compact and present only in alveolar spaces. The adjacent interstitium usually showed fibrous thickening although granulomas were absent. The granulomas contained central clefts surrounded by mononuclear and multinucleated giant cells, both of which were CD68 positive. The cells outside the granulomas and those lining the adjacent alveolar walls were AB1/AB3 and CAMS.2 positive and CD68 negative. The application of an extendeplectin panel demonstrated restricted glycoprofiles for multinucleated cells, alveolar macrophages and alveolar lining cells. The glycoprofiles of the first two were similar to each other, but were different from the third. Conclusion: The mononuclear and multinucleated cells of cholesterol cleft granulomas are derived from the macrophage-mononuclear cell lineage and express glycoproteins with a high mannose content. The alveolar lining cells are type II pneumocytes which do not contribute to the granuloma cell population.