The differential diagnosis of DMM includes
non-specific reactive pleural fibrosis, as seen in
some cases of tuberculosis, pleurisy, and
F rheumatoid disease.'4 Clinical history may be
helpful. Diffuse pleural fibrosis,'14-6 associated
with exposure to asbestos, has a basket weave
pattern with little inflammation and no cellular
fibroblastic proliferation. In all cases described
by Stephens et al'4 there was dense subpleural
parenchymal interstitial fibrosis and asbestos
fibre counts were very high. Localised pleural
plaques should not cause diagnostic difficulty
f as the basket weave arrangement is regular and
storiform or whorled areas are absent. Solitary
fibrous tumours of the pleura (fibrous mesothelioma)
are unrelated to asbestos exposure
f and are usually well circumscribed.4 1720 They
are composed of spindled cells resembling
fibroblasts and arranged in a haphazard,
sometimes storiform, pattern. Foci of necrosis
may be found, especially in larger tumours.
F The tumour cells are strongly positive for
vimentin and negative for keratin. This contrasts
with malignant mesothelioma where the
tumour cells are usually cytokeratin
positive.122 Though fibrous tumours of the
pleura resemble the desmoplastic areas of
DMM, the macroscopic appearances and
absence of keratin should indicate the correct
diagnosis of fibrous tumour where this is
considered. Primary sarcomas of the pleural
cavity are rare, and22 with occasional exceptions,
keratin negative.