Background: Sex cord-stromal tumors are rare tumors of the testis and are often seen in the pediatric age group. Case Presentation: Right testicular mass was detected in the ultrasonography of a 19-year-old male patient who complained of pain and enlargement of the testis for 2 weeks. Tumor markers such as β-human chorionic gonadotropin, lactate dehydrogenase, and alpha-fetoprotein were within normal levels. The patient was diagnosed as undifferentiated type sex cord-stromal tumor after orchiectomy. Conclusion: Undifferentiated-type sex cord-stromal tumors are characterized by proliferations of incompletely differentiated sex cord or stromal elements. In the literature, reported cases histologically have predominantly spindle cell areas, but we did not identify any spindle cell areas in our case. Due to the limited number of published studies of these cases, the estimation of their frequency and behavior is difficult and their diagnosis may be challenging.
Keywords: Sex cord-stromal tumor, testis, indeterminate differentiation, prognosis, malignancy potential.