Intratubular Teratoma: A Rare Form of Testicular Germ Cell Neoplasia.

Germ cell neoplasia in situ is the initial manifestation for invasive germ cell tumor. Further progression will result in intratubular germ cell tumor with the majority being intratubular seminoma or intratubular embryonal carcinoma. Intratubular teratoma in the testis is exceptionally rare with no well-documented cases to our knowledge. In this article, we report a case of an intratubular teratoma adjacent to mixed germ cell tumor in the testis. The patient is a 34-year-old male who presented with a palpable right testicular mass and underwent right radical orchiectomy. Gross examination of the testis revealed 2.0-cm tan, well-circumscribed, firm, and nodular mass at the inferior pole. Microscopic examination revealed a mixed germ cell tumor, predominantly seminoma (95%) with embryonal carcinoma (4%) and teratoma (1%). There is also germ cell neoplasia in situ, intratubular seminoma, and intratubular teratoma at the periphery of the tumor. Tubules with intratubular teratoma were filled by neoplastic squamous cells with a single layer of germ cell neoplasia in situ at the periphery. Adjacent to the intratubular teratoma was seminoma, embryonal carcinoma, and invasive teratoma. Immunohistochemical stains showed the neoplastic squamous cells in the tubule to be positive for p40 and negative for OCT34 and D2-40. The single layer of germ cell neoplasia in situ at the periphery of the intratubular teratoma was negative for p40 and positive for OCT34 and D2-40. Although teratoma is a common component in an adult germ cell tumor, an intratubular manifestation is exceptional. The present case illustrates this rare finding.