Diffuse malignant mesothelioma of the pleura: a clinicopathological study of six patients with a prolonged symptom-free interval or extended survival after biopsy and a review of the literature of long-term survival.

Diffuse malignant mesothelioma of the pleura generally proceeds rapidly with clinical deterioration soon after the initial histopathological diagnosis of the tumor. We encountered six patients in whom the symptom-free interval after biopsy was surprisingly prolonged. Histopathologically, the tumor in each case was epithelioid with prominent myxoid stroma and formation of tubules and micropapillae. Cytologically, the malignant cells had relatively regular nuclei with bland chromatin. As individual findings, these histological and cytological features are common in diffuse malignant mesothelioma. However, the combination of (1) bland cytology of epithelioid cells, (2) formation of tubular and micropapillary patterns, (3) a myxoid stroma and (4) an absence of sclerosing desmoplasia, as observed in these six cases, might indicate indolent disease at the outset in a few patients. It is possible that these features are related to early stage of disease rather than having discriminatory value in their own right. We do not conclude that initially restrained disease necessarily presages a longer mean survival because the follow-up in these patients has not been long enough. We present these observations because, to date, this malignancy has proven so refractory to clinical management.