Simultaneous occurrence of a rectal carcinoma and a diffuse well differentiated papillary mesothelioma of the peritoneum.

Diffuse well differentiated papillary mesothelioma is a rare neoplasms of the peritoneal cavity which has generally been regarded as a tumor with low-grade malignant potential [1-4]. The well differentiated papillary mesotheliomas reported in recent literature are considered as border line lesions with a long term benign clinical course. There are however, only few studies with small numbers of diffuse well differentiated mesotheliomas [1, 2, 5, 6]. The synchronous appearance of such a lesion with a second malignancy therefore is a very rare event. Such a clinical scenario would suggest diffuse tumor spread to the peritoneum resulting in an inappropriate palliative procedure alone-being undertaken. To our knowledge this is the first report of the simultaneous occurrence of a rectal carcinoma in combination with a diffuse well differentiated papillary mesothelioma of the peritoneum.