[A Case of Prepubertal-Type Teratoma in a Male Adult : Importance of a Definitive Diagnosis by the Fish Method].

Teratomas are broadly classified according to the presence or absence of germ cell neoplasia in situ (GCNIS), which is defined as neoplastic germ cell proliferation in the seminiferous tubules. Postpubertaltype teratoma is classified into a germ cell tumor derived from GCNIS, and it is malignant in adults. However, a prepubertal teratoma is classified as a germ cell tumor unrelated to GCNIS. It is common in children and has a benign course. We report a case in a 60-year-old man who had been aware of a nodule in his left scrotum for 15 years, and felt heaviness and pain from a few months before he visited a specialist. He visited a local urologist and was referred to our department under the diagnosis of a left testicular tumor in February 202X. In March 202X, he underwent a left high orchiectomy. A 12×5 mm white mass lesion was observed, and a pathological examination showed intestinal epithelial and bronchial epithelial structures. Additionally, no GCNIS was found in background seminiferous tubules. There was no amplification of chromosome 12 short arm as shown by the fluorescence in situ hybridization method. On the basis of these pathological findings, prepubertal-type teratoma was diagnosed in this patient.