Proteus syndrome is a very rare and complex disorder with malformations and overgrowth of multiple tissues. This disorder was designated Proteus syndrome by Wiedemann et al. to denote its variable clinical expression. Our patient presented with macrodactyly, cerebriform appearance and a huge abdominal mass. A biopsy under laparotomy was performed, and histopathological examination revealed myelolipoma. Tumor resection was performed. To our knowledge, no case of Proteus syndrome presenting a myelolipoma in the retroperitoneal cavity has been reported before.