OBJECTIVETo investigate histomorphological feature of silicotic nodules under Warthin-Starry (WS) silver staining and its value in the histopathological examination.

METHODSSix cases with silicosis obtained by autopsy and 21 cases with sarcoidosis were collected (among which 3 cases were obtained by autopsy and 18 cases were obtained by biopsy). The serial sections of those paraffin embedded samples were applied respectively for (1) hematoxylin and eosin (HE) staining, (2) WS staining, (3) streptomyces avidin-peroxidase (SP) immunohistochemical staining for mouse anti-human CD68 monoclonal antibody, (4) observing under transmission electron microscope (TEM), (5) X-ray spectrum chemical element analysis(X-RSA). The emphasis of observation and analysis were the dust particles in silicotic nodules and granulomas cells (dust cells, epithelioid cells and multinucleated giant cells in the granulomas). The dust particles deposit in the granulomas were graded under the HE and WS staining.

RESULTSUnder the HE staining the dust particles deposit degrees were (+++) in cellular silicotic nodules, (+) in the fibrous ones, and (-) in the sarcoid nodules; under the WS staining and the dust particles deposit degrees were (+++) in both silicotic nodules whose dust particles were characteristically black, and (+/++) in sarcoid nodules. The dust particles deposit degrees in silicotic nodules were markedly higher than those in sarcoidosis (P < 0.01). The results of immunohistochemical staining indicated that the expression of CD68 in both cells of silicotic nodules and sarcoid nodules were positive. The positive degrees decreased successively with the content of the dust particles. The dust particles of silicotic nodules could be more readily observed than those of sarcoidosis in size and electronic density under TEM. The results of X-RSA indicated that the main chemical element in both dust particles was silicon.

CONCLUSIONWS staining is better than HE staining in showing the dust particles of silicotic nodules, which appear characteristically black, especially in the fibrous ones. Together the TEM observation and X-RSA, the silicotic nodules may be prompted.