Objective To evaluate the pathological,histochemical and clinical features of primary clear cell carcinoma of the epididymis,and to investigate its diagnosis,treatment and prognosis.Methods The clinical data of one case of primary clear cell carcinoma of the epididymis were reported and the relevant literature was reviewed.Results The patient was a 43-year-old man presenting with a painless mass in the left epididymis.On physical examination,a 1.0 cm-sized smooth solid nodule on the head of left epididymis could be palpated without tenderness.Then the patient underwent left epididymectomy.On postoperative histopathological study,the tumor was characterized by diffuse sheets of clear cells and adenoid structures.Immunohistochemical assay showed AE(++),AE3(+/-),NSE(-) and interstitialoma(-) in the tumor tissues.Postoperatively,MRI showed no space-occupying lesion in both kidneys,and B-ultrasound indicated no abnormality of the bladder.Fifteen days after operation,left orchiectomy was performed on the patient.Pathology showed no clear cell carcinoma tissue of the testis.Follow-up was 15 months.The patient was reported to be alive and tumor-free.Conclusions The histogenesis of primary clear cell carcinoma of epididymis is unclear yet.The diagnosis depends on pathologic studies,and should be differentiated from nephrogenic adenoma and metastatic carcinoma.Radical surgery is the main treatment choice.