[Mesotheliomas with leucocytic infiltration]

Malignant mesotheliomas are rare tumors which can affect pleura, peritoneum, pericardium, or tunica vaginalis testis. Histomorphologically, predominant epitheloid, sarcomatoid and biphasic types can be distinguished. In some cases, leucocytic infiltrations can be observed adjacent to the tumor. Here, mesotheliomas presenting inflammatory reactions to tumor growth have to be differentiated from occasional cases with parasynchronic development of neoplastic lymphatic diseases. Moreover, so called lymphohistiocytoid mesotheliomas, a sporadically observed variant of malignant mesotheliomas, have been reported to imitate inflammatory patterns. These different forms of malignant mesotheliomas are difficult to distinguish and may lead to diagnostic misinterpretations and consequently therapeutic mismanagement. The purpose of this study was to differentiate morphological and immunohistochemical characteristics of the above mentioned diagnoses. We therefore studied two rare cases, a mesothelioma with parallel lymphoma and a lymphohistiocytoid mesothelioma, and compared them to a third more common case of mesothelioma with inflammatory tissue-reaction.