A rare case of primary germinoma in corpus callosum.

Background Primary intracranial germinoma is a rare lesion which accounts for approximately 0.5–2% of all central nervous system (CNS) tumors. Generally, this neoplasm occurs in the midline structures with the majority located in the pineal and suprasellar regions. Germinoma presenting primarily in the corpus callosum is highly unusual and reportings of similar cases in scientific literature are limited. The aim of this case report is to describe clinical features, imaging findings, and management of a primary germinoma uniquely presenting in the corpus callosum. Case Information 21-year-old man with Parinaud syndrome, gait instability, altered mood, and remote history of orbital trauma presented initially for an ophthalmology evaluation of vision change. These symptoms prompted intracranial imaging, including MRI which revealed an enhancing lesion in the corpus callosum, evidence of obstructive hydrocephalus, and an arachnoid band in the region of the aqueduct of Sylvius. The lesion was believed to potentially represent either a primary CNS lymphoma, glioblastoma, anaplastic astrocytoma, or tumefactive demyelinating disease. The patient underwent a right frontal stereotactic brain biopsy and third ventriculostomy. Pathologic evaluation with immunohistochemistry and tumor marker analysis confirmed a diagnosis of primary germinoma. Post-operative plan included oncology consultation to establish chemotherapy and radiation treatment. Additional imaging showed corpus callosum mass with evidence of diffuse extension in the surrounding structures. Interestingly, in contrast to pre-operative imaging, enhancement of the pineal gland area was noted and provided additional rationale for development of obstructive hydrocephalus. Conclusion Primary germinoma of corpus callosum has not yet been extensively described in literature. The present case demonstrates that primary germinoma can occur in uncommon midline structures and present with unique imaging findings. This report contributes to improving recognition and further understanding of clinical presentation and course and potentially to optimize the treatment in similar future case.