Unresectable Metastatic Testicular Germ Cell Tumor With Low-grade Neuroglial Neoplasm, Stable After Radiation and...

We present an 18-year-old male patient who presented with a 16 cm testicular tumor alongside multiple lesions in the lungs, right pelvis with involvement of the ischio/pubic bone, and enlarged pelvic lymph nodes on imaging, suspicious for metastatic disease. Histologic and immunohistochemical examinations revealed an embryonic type neuroectodermal tumor (somatic-type malignancy, 10%) arising in a malignant mixed germ cell tumor composed of teratoma (50%), embryonal carcinoma (10%) and yolk sac tumor (30%). After treatment with chemotherapy and radiation, repeat imaging demonstrated a right pelvic sidewall mass that decreased in size from 40 mm at 11 months after the initial diagnosis to 18 mm at 22 months after the initial diagnosis. A right pelvis medial thigh wall mass that had a lytic bone component showed a slight increase in size from 151 mm at 11 months after the initial diagnosis to 154 mm at 22 months after the diagnosis. On biopsies performed at 3, 10, and 26 months after the initial diagnosis, this lytic lesion consistently demonstrated a neoplasm composed of low-grade neuroglial differentiation. This is the first case in the medical literature where a residual malignant germ cell tumor consisting of low-grade neuroglial neoplasm is in a site that is not amenable to resection without significant morbidity. The tumor initially regressed with the traditional first-line chemo-radiotherapy regimen but regrew and stabilized with a second regimen of chemotherapy. The clinical course of this case invites consideration for an active surveillance approach in cases with similar characteristics.