Tumefictive MS (Video)

Right frontal brain biopsy revealed markedly atypical cells arranged in discohesive sheets with large central nuclei and prominent nucleoli on a background of lymphocytic infiltrate. Immunohistochemical stains were diagnostic of germinoma. Repeat lumbar puncture demonstrated a lymphocytic pleocytosis (16 cells/mm3) with negative B-HCG and AFP supporting a diagnosis of germinoma. Systemic chemotherapy with carboplatin and etoposide was initiated. Craniospinal radiation is planned. Germinomas are the most common type of germ cell tumor and 90% arise in patients under the age of 20. Typical locations include pineal and suprasellar regions (including the infundibulum). While the imaging features of our case are consistent with germinoma, tumefactive demyelinating lesions, gliomas, glioneuronal tumors and inflammatory lesions (eg. neurosarcoidosis) can appear similarly. There are fewer than 10 reported cases radiologically similar to ours of germinoma involving the corpus callosum without extension from a more typical location or additional CNS lesions. Not only was the site of the initial lesion highly unusual for germinoma, but the CSF studies were also supportive of an inflammatory process, leading the neurologist to make an incorrect diagnosis of MS. However, these CSF characteristics are not specific for MS and can also be seen in response to malignancy, including germinoma. The clinical course, including lack of painful vision loss and lack of visual recovery, were also inconsistent with a diagnosis of MS. In retrospect, the development of diabetes insipidus (DI), 3 years prior to our patient's vision loss, was the first symptom of germinoma despite negative imaging at the time of her DI diagnosis. Although a normal pituitary infundibulum reduces the risk of malignancy, endocrine abnormalities may precede infundibulum abnormalities by years and diagnosis of germinoma by years more. This underscores the importance of surveillance imaging in patients with presumed idiopathic DI.