[Roentgenologic evaluation of indrawn parietal pleura]

Among linear densities extending out from the lateral margin of a peripheral mass to the pleural surface, a thin line with a small triangular density at the pleural surface is considered to be contiguous layers of indrawn visceral pleura with a small amount of fluid between layers. We agree that the thin line represents contiguous layers of indrawn visceral pleura, but we believe that the triangular density at the pleural surface is not formed by a small amount of pleural effusion, but by indrawn parietal pleura accompanying extrapleural soft tissue of the chest wall. A trapezoid or a belt shaped soft tissue density between a peripheral mass contiguous to the visceral pleura and the chest wall are also signs of indrawn both visceral and parietal pleurae in the presence of adhesion of the pleura over the mass.