原發性副睪淋巴癌是一種罕見的疾病。一位69歲男性因為左側副睪發現無痛性腫塊至本院求治。放射診斷科醫師根據超音波影像認為是良性的發炎反應。由於臨床上，病人已屆高齡且並無發燒及不正常尿道分泌物，亦無解尿疼痛等發炎感染症狀。於是懷疑此腫塊有惡性的可能。手術中發現左側副睪被黃色腫瘤所均勻浸潤，最後我們為病人施行根除性睪丸切除手術。經過病理切片及一系列的檢查，證實為原發性副睪淋巴癌。我們將於本文中介紹此病例臨床及病理上的特徵，並詳述超音波上的異常表現。

A primary epididymal lymphoma is a rare disease. A 69-year-old man presented with a painless mass over the left epididymis. A benign inflammatory process was diagnosed via ultra-sonography by radiologists. Because of the advanced age of the patient and the lack of symptoms such as fever, urethral discharge, and dysuria, malignancy of the left epididymal mass was suspected. During the operation, a yellowish tumor infiltrating the entire epididymis was noted, and a radical epididymo-orchiectomy was then performed. Through pathological examination and a series of staging studies, primary epididymal lymphoma was proven. We describe the clinical and pathological features and unusual findings of the sonographic appearance of this disease.