Malignant peritoneal mesothelioma(MPM) is a rare tumor that develops in the peritoneum.In this paper,we describe an extremely rare case of MPM metastasizing to the appendix in a 48-year-old female who initially presented with a persistent high fever.The woman reported a slight lower abdominal discomfort which had been relieved by urination for four months.She had lost 5 kg of weight.There was no nausea,vomiting,diarrhea,ab-dominal pain,or abdominal distension.Many broad spectrum antibiotics were given without relief of fever.Computed tomography(CT) scans revealed a thickened omentum majus and diffused multiple omental nodules.An omentec-tomy,appendectomy,and adnexectomy were carried out.A gross pathologic specimen of omentum tissue revealed a firm gray-white mass.Microscopic and immunohistochemical examinations confirmed the diagnosis of appendiceal and bilateral adnexal metastases of an MPM.These results suggest that MPM should be considered in the differential diagnosis of unexplained persistent high fever.Awareness of such atypical presentations of mesothelioma may help to make a correct diagnosis. Malignant peritoneal mesothelioma (MPM) is a rare tumor that develops in the peritoneum. In this paper, we describe an extremely rare case of MPM metastasizing to the appendix in a 48-year-old female who initially presented with a persistent high fever. woman reported a slight lower abdominal discomfort which had been relieved by urination for four months. had had lost 5 kg of weight. where was no nausea, vomiting, diarrhea, ab-dominal pain, or abdominal distension. Many broad spectrum antibiotics were given without relief of fever. Computed tomography (CT) scans revealed a thickened omentum majus and diffused multiple omental nodules. Ann omentec-tomy, appendectomy, and adnexectomy were carried out. A gross pathologic specimen of omentum tissue revealed a firm gray-white mass. Microscopic and immunohistochemical examinations confirmed the diagnosis of appendiceal and bilateral adnexal metastases of an MPM. These results suggest that MPM should be considered in the differential diagnosis of unexplaine d persistent high fever. Awareness of such atypical presentations of mesothelioma may help to make a correct diagnosis.