'Black spots' and hyaline pleural plaques on the parietal pleura of 150 urban necropsy cases

The absence of any direct connection between the lung and the parietal pleura raises questions about the mechanisms of pleural migration and retention of inhaled particles. It has been suggested that specific areas of parietal pleura absorb and retain inorganic particles from the pleural space, including carbon pigments and asbestos fibers, and could be starting points for pathologic changes induced by mineral fibers. These particle-collecting structures have been called "black spots." To study their distribution, macroscopic appearance, and possible relationship with pleural plaques, the parietal pleura of 150 consecutive necropsies of urban dwellers (mean age 67.7 +/- 12.9 years) were examined. The size and intensity of spots were scored and recorded on a computer scheme together with information of the presence of pleural plaques. Black spots were observed in 92.7% of the cases. They were mainly located in the lower costal and diaphragmatic zones and could correspond to the anatomic distribution of structures involved in pleural cavity clearance. Scores correlated with sex and age. There was no relationship between the predominant locations of black spots and hyaline pleural plaques.