Am. J. Respir. Crit. Care Med., Vol 153, No. 1, Jan 1996, 444-449.
Black spots concentrate oncogenic asbestos fibers in the parietal pleura. Thoracoscopic and mineralogic study
C Boutin, P Dumortier, F Rey, JR Viallat and P De Vuyst
Pneumology Department, Concneption Hospital, Marseilles, France.
Epidemiologic and pathologic data demonstrate that malignant mesothelioma
occurs preferentially after exposure to long amphibole asbestos fibers.
However, mineralogic studies have rarely detected such fibers in the
parietal pleura. We hypothesized that the distribution of asbestos fibers
in the pleura was heterogeneous and that they might concentrate in certain
areas, as does coal dust in patients showing anthracotic "black spots" of
the parietal pleura during thoracoscopy. We collected thoracoscopic biopsy
samples from these black spots and from normal areas of the parietal pleura
and lung from 14 subjects (eight with and six without asbestos exposure).
Asbestos content was determined by transmission electron microscopy. In
exposed subjects, mean fiber concentrations were 12.4 +/- 9.8 x 10(6)
fibers/g of dry tissue in lung, 4.1 +/- 1.9 in black spots, and 0.5 +/- 0.2
in normal pleura. In unexposed patients, concentrations were 0, 0.3 +/-
0.1, and 0, respectively. Amphiboles outnumbered chrysotile in all samples.
A total of 22.5% of fibers were > or = 5 microns in length in black
spots. A histologic similarity of these black spots with milky spots is
suggested by conventional and electron microscopy. We conclude that the
distribution of asbestos fibers is heterogeneous in the parietal pleura.
Indeed, the fibers concentrate in black spots, where they can reach high
concentrations. These findings could explain why the parietal pleura is the
target organ for mesothelioma and plaques.
