Objective:Well-differentiated papillary mesothelioma is an uncommon subtype of mesotheli-oma with a frequently indolent course, although it occasionally manifests in a more aggressive form. To establish a treatment strategy for this rare disease, we report the clinical characteristics and outcomes of 15 patients with well-differentiated papillary mesothelioma. Methods: All pathologically diagnosed well-differentiated papillary mesothelioma cases were reviewed between 1998 and 2012. Results: Of the 15 cases, 8 and 7 presented with single and multiple lesions, respectively. All cases with single lesions were asymptomatic, while 4 out of the 7 cases with multiple lesions were symptomatic. After tumor excision, none of the eight single-lesion cases experienced tumor recurrence. Among the other seven cases with multiple lesions, only one patient with dis-seminated lesions died due to disease burden. Five patients with multiple lesions received cis-platin-based intravenous or intraperitoneal chemotherapy, with a mix of complete (n 2) and partial (n 2) responses observed. Of particular note, one patient receiving cisplatin and peme-trexed combination chemotherapy experienced complete tumor resolution without any serious toxicity.