THE DIAGNOSIS OF DESMOPLASTIC MALIGNANT MESOTHELIOMA AND ITS DISTINCTION FROM FIBROUS PLEURISY - A HISTOLOGIC AND IMMUNOHISTOCHEMICAL ANALYSIS OF 31 CASES INCLUDING P53 IMMUNOSTAINING

We studied 31 patients with fibrotic pleural lesions and classified th em as desmoplastic malignant mesothelioma (DMM) or fibrous pleurisy (F P) using predetermined histologic criteria, including a paucicellular fibrotic pleural lesion with a storiform pattern or the ''patternless pattern'' of Stout, plus 1 or more of the following: invasion of chest wall or lung, bland necrosis, frankly sarcomatoid areas, and distant metastases. Staining for p53 was performed in 22 cases. Follow-up was obtained on all cases and compared with the histologic diagnoses. For 24 cases, the consensus diagnosis was DMM; 19 of these displayed frank ly sarcomatoid areas, 16 showed invasion, and 8, bland necrosis. Of th e 24, 23 patients died of disease and 1 was alive with disease. The re maining 7 cases were classified as FT, and all were alive without dise ase. The concordance among 3 pathologists using the criteria was excel lent. Staining for p53 was more common in DMM than in FP, but the diff erence was not statistically significant. The concordance in interpret ing the p53 stains by the same 3 pathologists was moderate. The distin ction between DMM and FP in a predominantly fibrotic pleural lesion ca n be made in most cases with adequate sampling and the use of specific criteria.