Objective:To investigate the clinical characteristics,treatment and prognosis of primary pe-noscrotal extra-mammary Paget’s disease (PSPD).Methods:The clinical and pathological data of 22 cases of primary PSPD were retrospectively reviewed.Survival rate of the overall patients,the invasive patients,and the patients with positive surgical margin or negative surgical margin were analyzed with Ka-plan-Meier survival curve method.Results:Among all the patients with primary PSPD,the median age of onset was 64.5 (39 -84)years,the median time of disease duration was 40 (2 -300)months,and the median long diameter of lesion was 4.75 (1 -10)cm.In the study,12 patients (54.5%)were in pathological stage A1,6 patients (27.3%)were in pathological stage A2,and 4 patients (18.2%) were in pathological stage B.Scrotum and penile of most patients (n =12,54.5%)were involved,5 patients (22.7%)were scrotum only,and 5 patients (22.7%)were penile only.Erythema (n =18, 81.8%),itchiness (n =16,72.7%),ulcerate (n =12,54.5%),exudation (n =11,50.0%),and pain (n =4,18.2%)were the major manifestations.All the patients with primary PSPD were treated with wide surgical excision.The rate of invasive patients was 77.3% (n =17).Of them,6 patients had positive surgical margin.The surgical margins of non-invasive patients were all negative.Twelve patients exhibited local recurrence or/and metastases,and the status of surgical margins (P =0.015)and the depth of invasion (P =0.010)were important risk factors.Inguinal lymph nodes were generally in-volved.The difference of the delay of diagnosis between metastasis and non-metastasis was significant (P =0.040).The 5-year survival rates of the overall and invasive patients were 33.7% and 27.9%, respectively.The patients with positive surgical margin had poor prognosis.Conclusion:Primary PSPD, with the characteristics of long duration,high invasive tendency and high incidence of local recurrence or metastases,generally occurs in the elderly.Surgery should be performed at first.The delay of diagnosis, positive surgical margins and the involvement of inguinal lymph node are important risk factors.Biopsy, frozen section and inguinal lymph node biopsy (ILNB)can standardize diagnosis and treatment.