Case of seminoma with possible spontaneous regression without extragonadal metastatic lesion

We present an extraordinarily rare finding of a testicular seminoma apparently in the process of spontaneous regression without accompanying metastatic lesion. A 35-year-old man visited our institute for persistent scrotal induration after the administration of antibiotics for several weeks. Ultrasonography and magnetic resonance imaging showed a capsulized tumor in his left atrophic testicle, without other visceral tumor or lymphadenopathy. We performed left radical orchiectomy. Histological examination revealed a fibrotic tumor with a small area of pure seminoma apparently undergoing spontaneous regression, and an intratubular germ cell neoplasia, unclassified, occurring diffusely. The patient is free of disease at 1 year after surgery.