Malignant mesothelioma is rare, and its prognosis is markedly poor. It is often difficult to distinguish malignant mesothelioma from carcinomatous peritonitis of other solid tumors. We report a case of malignant peritoneal mesothelioma diagnosed by a laparoscopy with the consent of her and her family. A 68-year-old Japanese woman, who indicated ascites, multiple abdominal masses, and a high level of CA125, was referred to our hospital. The ascites cytology by conventional smear and cell block technique were all negative. We evaluated the abdominal wall adhesion around the umbilicus using abdominal ultrasonography and considered we could safely perform a looking laparoscopy. The laparoscopy revealed peritoneal thickening and multiple white nodules on the greater omentum, liver, diaphragm, and uterus. The biopsy was performed from the greater omentum and peritoneum. In histopathological examination, atypical eosinophilic cells were observed and calretinin and D2-40, both known as mesothelial markers, were positive. She was diagnosed with malignant peritoneal mesothelioma and treated with six cycles of carboplatin, pemetrexed, and bevacizumab therapy followed 30 cycles of pemetrexed and bevacizumab as maintenance therapy, of which therapeutic efficacy was the complete response. A looking laparoscopy is effective for the diagnosis of malignant peritoneal mesothelioma.
