Thalamic germinoma: a challenging diagnosis, case report and literature review

Implantation Metastasis Following a Biopsy of Thalamic Germinoma: A Case Report

Germ cell tumors (GCTs) commonly develop in the pineal and suprasellar regions, with the most common GCTs being germinomas. In this report, a 22-year-old male presented with progressive right-sided weakness, and his imaging was consistent with a left thalamic high-grade glioma. A stereotactic biopsy was performed, revealing a germinoma, but radiation therapy was not done, and the patient was lost to follow-up. He was readmitted due to ulcerative tumor growth at the previous skin incision, and imaging revealed tumor progression with implantation metastasis along the track of the previous biopsy. The scalp lesion and tumor through the burr hole were excised, and histopathologic studies confirmed that it was a proliferation of the previous germinoma. He was discharged well but was unfortunately unable to follow up at the clinic. Thalamic germinomas are difficult to diagnose and treat because of their rarity. Here, we underscore the importance of careful patient selection, precise biopsy techniques, thorough postoperative management, and close radiographic surveillance to minimize the risk of implantation metastasis and promptly treat it if it occurs.

Ectopic Germinoma: A Delayed Diagnosis With Serial Magnetic Resonance Imaging Features

Germinoma arising from intracranial off-midline structures is considered ectopic. Although basal ganglia germinoma is a rare occurrence, it is more commonly seen in the Asian population, particularly among boys. Here, we report a case of an adolescent boy who presented with hemiplegia and delayed diagnosis of basal ganglia germinoma with progression on serial magnetic resonance imaging (MRI). Several signal changes have been described during the early stage of the disease such as T2-weighted patchy hyperintense signal, cerebral hemiatrophy, and signal change on susceptibility-weighted imaging. ¹¹C-methionine positron emission tomography is an additional imaging technique that can reveal ectopic germinoma. Follow-up MRI revealed small cystic changes, and the latest imaging showed progression into a large multicystic lesion with mass effect. The patient underwent surgery, and histopathological examination revealed basal ganglia germinoma. We highlight the serial MRI changes that were suggestive of basal ganglia germinoma in this case.