Benign multi-cystic peritoneal mesothelioma (BMCM) is a very rare disease (about 150 cases observed). The aetiology is currently little-known, and the data collected, without having achieved conclusive re sults, identify two possible causes: neoplastic and reactive inflammatory. This case report refers to a recidivism of BCMC in a patient whose brother, few months before, underwent a left nephrectomy and right renal Radio Frequency Termo Ablation (RFTA) for bilateral papillary renal cell carcinoma. For the recurring trend, the onset in a male young patient without chronic inflammatory diseases evidence, the presence of a first degree relative with a rare carcinoma we supposed a neoplastic aetiology. The available literature suggests that both tumours (BCMC and renal cell carcinoma) are susceptible to oestrogens. This biomolecular mechanism could represent a valid antipathogenic hypothesis.