Impact on Survival of Nuclear Atypia in Epithelioid Malignant Mesothelioma

Introduction: Malignant pleural mesothelioma is a rare tumour with a bad prognosis. The only consensual prognostic factors are represented by the stage and the histologic type. Concerning the histologic type, epithelioid mesothelioma is known to have better prognosis in comparison with the sarcomatoid and biphasic types. Epithelioid mesotheliomas have been reported to be a heterogeneous prognostic group. Our aim was to assess the impact on the survival of different characteristics of epithelioid mesothelioma, including nuclear atypia, mitotic count, MIB-1 index, inflammatory host response, stromal desmoplasia, necrosis, vascular emboli and invasion depth. Material and methods: We performed a study of survival of 30 malignant pleural mesotheliomas according to the different parameters studied. Results: The study included 26 women and 4 men. The mean age of the patients was 61 years. The microscopic exam concluded to an epithelioid mesothelioma in 17 cases, sarcomatoid mesothelioma in 4 cases and biphasic mesothelioma in 9 cases. The 17 cases of epithelioid mesothelioma developed severe nuclear atypia in 6 cases and mild nuclear atypia in 11 cases. The mitotic count and the MIB-1 score were respectively inferior to 5 mitoses/50 HPF and inferior to 10% in 11 cases and were superior to 5 mitoses/50 HPF and superior to 10% in 6 cases. No vascular emboli were recorded. Tumour necrosis was reported in 1 case. The inflammatory host response was severe in 4 cases and mild in 13 cases. The tumoral stroma was desmoplastic in 4 cases. The invasion depth was superior to 0.5 mm in 16 cases. The median overall survival amounted to 180 days. Nuclear atypia was the only feature that had impact on survival in the group of epithelioid mesothelioma. Conclusions: Our results highlight the correlation of nuclear atypia with survival.