Abstract： Objective:To investigate the clinicopathological features and prognosis of mycosis fungoides.Methods:The clinical data of 34 patients with mycosis fungoides hospitalized in Liaoning Cancer Hospital from January 1996 to December 2016 were retrospectively analyzed. The clinicopathological characteristics and prognosis of the patients were summarized. The follow-up was up to June 2021. Kaplan-Meier method was used for survival analysis, and log-rank test was used to compare the overall survival (OS) of patients among different subgroups.Results:Among the 34 patients, 22 (64.7%) were male and 12 (35.3%) were female; the median onset age was 56.5 years (25-93 years). A total of 23 cases (67.6%) presented with the rash on the whole body, and the main manifestations of the rash in the tumor stage were tumor rupture (10 cases, 29.4%) and redness (7 cases, 20.6%); 20 cases (58.8%) were misdiagnosed at initial onset. In the terms of TNMB stage, 3 cases were at stage Ⅰ (8.8%), 11 cases were at stage Ⅱ(32.4%), 3 cases were at stage Ⅲ (8.8%), and 17 cases were at stage Ⅳ (50.0%); 17 cases (50.0%) had the lesions confined to the skin and 17 cases had distant metastasis. Among the patients with distant metastasis, 7 cases had visceral organs involvement, 5 cases had lymph nodes involvement, and 5 cases had bone marrow or peripheral blood involvement. There were 32 cases treated with first-line chemotherapy alone, 9 cases with radiotherapy alone, and 7 cases in combination with radiotherapy and chemotherapy. Among the 32 patients treated with first-line chemotherapy, 14 cases had complete remission (CR), 12 cases had partial remission (PR), and response rate (RR) was 81.3% (26 cases); among the 9 patients who received radiotherapy, 3 cases had CR, 5 cases had PR, and RR was 88.9% (8 /19). The median follow-up time was 142.5 months; until the last follow-up, 20 (58.8%) cases survived, 6 (17.6%) cases died and 8 (23.5%) cases lost the follow-up. Survival analysis showed that the median OS of the whole group was not reached. Compared with patients whose lesions were confined to the skin, patients with distant metastasis had poorer OS ( P = 0.039). Among patients with distant metastasis, those with lymph node involvement had better OS, followed by those with bone marrow or peripheral blood involvement, those with visceral organ involvement had the poorest OS ( P = 0.045). Conclusions:The clinical misdiagnosis rate of early-stage mycosis fungoides is high, and the diagnosis mainly depends on clinical, histological and pathological characteristics. Radiotherapy and chemotherapy have high efficiency for early-stage disease and the prognosis of patients with distant metastasis is poor. OS in patients with lymph node involvement is better than that in patients with bone marrow or peripheral blood involvement, and OS in patients with visceral organ involvement is the worst.