Metastatic "Burned Out" Seminoma Causing Neurological Paraneoplastic Syndrome-Not Quite "Burned Out"

Abstract

A 44-year-old man presented with cerebellar ataxia and limbic encephalitis and was ultimately diagnosed with metastatic germ cell neoplasm resulting from a "burned out" primary testicular tumor. The patient had progressive ataxia, leading to a thorough investigation for infectious, autoimmune, metabolic, and malignant causes of acquired cerebellar ataxia that revealed no significant findings. Testicular sonography demonstrated a possible right testicular lesion that was not confirmed on radical inguinal orchiectomy. F18-FDG positron emission tomography/computerized tomography scan revealed a solitary retroperitoneal lesion, concerning for metastatic disease but not amenable to percutaneous biopsy. A robotic retroperitoneal lymph node dissection was performed and pathology revealed a CD117-positive metastatic seminoma leading to appropriate germ cell tumor-directed chemotherapy. After completing chemotherapy and during 1 year of follow-up, there has been a gradual improvement of the patient's neurological manifestations.

Keywords: burned out tumor; cerebellar ataxia; germ cell tumor; limbic encephalitis; testicular cancer.

Figure 1

(A) Sagittal T1 image shows vermian atrophy (arrow) and (B) axial FLAIR image shows right hippocampal hyperintensity (arrow). (C) Right testicular US showing a 9 mm × 7 mm hypoechoic lesion (arrow) with microcalcifications. (D) F18-FDG positron emission tomography/computerized tomography showing an FDG-avid 1.4-cm × 0.9-cm lymph node in the periaortic chain (arrow).

Figure 2

(A,B) Testis, hematoxylin and eosin stain: scarred area with hyalinized tubular Ghosts (lack arrow), increased vascularity and coarse calcifications (red arrow) within tubular profiles. No viable tumor was identified. (C) Lymph node, hematoxylin and eosin stain: small foci of metastatic GCT with seminomatous component (black arrows) with associated granulomas (red arrow head). (D) Immunohistochemical reactivity in tumor cells for CD117 support the diagnosis. CD30 (not shown) is negative.