Proton MR spectroscopy and diffusion-weighted imaging of intracranial germ cell tumors: Implications for differentiation from other lesions

Prognostic implications of distinctive imaging characteristics in primary intracranial germ cell tumors: A retrospective analysis

PURPOSE

Primary central nervous system (CNS) germ cell tumors (GCTs) are rare brain tumors that encompass two subtypes: germinomas and non-germinomatous germ cell tumors (NGGCTs), NGGCTs have less favorable outcome and require multi-modality treatment. Biopsy is recommended for disease diagnosis, the specimen may not adequately reflect the entire tumor. This study aimed to assess distinct imaging characteristics to differentiate between GCT subgroups and to identify possible initial image and subgroup features that influence survival.

METHOD

This retrospective study, conducted from January 2006 to March 2023, analyzed patient data and MRI findings of primary CNS GCTs. It evaluated tumor characteristics including cysts, seeding, multifocality, and hemorrhage. Tumor volumes and apparent diffusion coefficient (ADC) values of both tumoral and normal-appearing contralateral white matter were measured. These factors were correlated with overall and 5-year survival rates.

RESULTS

This study included 51 participants with CGTs, comprising 19 germinoma and 32 NGGCTs cases. GCTs with hemorrhage had worse overall (P = 0.03) and 5-year (P = 0.01) survival rates. No survival difference between germinoma and non-hemorrhagic NGGCT. NGGCTs were more likely to bleed (P < 0.001) than germ cell tumor, especially those with choriocarcinoma or yolk sac tumor components (P = 0.001). The ADC ratios of germinomas were significantly lower than those of NGGCTs (P = 0.03 for whole tumor; P < 0.01 or solid part), The ADC ratios of choriocarcinoma were also lower than mixed tumor (P = 0.01; P = 0.02).

CONCLUSION

Hemorrhage indicates worse prognosis. Intratumoral hemorrhage and ADC ratios differentiate germinoma from NGGCTs. Larger cohorts and advanced MR techniques are needed for future study.

Pretreatment diagnosis of suprasellar papillary craniopharyngioma and germ cell tumors of adult patients

BACKGROUND AND PURPOSE

Suprasellar papillary craniopharyngiomas and germ cell tumors in adults share some clinical and imaging similarities but have different therapeutic strategies and outcomes. This study aimed to evaluate the pretreatment diagnosis of these 2 tumors to improve the therapeutic outcome.

MATERIALS AND METHODS

We retrospectively enrolled 18 adults with papillary craniopharyngiomas and 17 with germ cell tumors. The MR imaging findings were evaluated, including signal change and anatomic extension. The medical records were reviewed to collect clinical findings, management, and outcomes.

RESULTS

The clinical findings of papillary craniopharyngiomas versus germ cell tumors were as follows: age: 46 ± 13.9 years versus 23 ± 7.1 years (P < .0001); diabetes insipidus: 2/18 (11%) versus 11/17 (65%) (P = .001); recurrence 13/16 (81%) versus 4/17 (24%) (P = .0031). The MR imaging findings of papillary craniopharyngiomas versus germ cell tumors were as follows—pituitary stalk thickening: 1.6 ± 0.4 mm versus 5.4 ± 4.2 mm (P < .0001); vertical infundibular extension: 1/18 (6%) versus 16/17 (94%) (P < .0001); sagittal spheric shape: 17/18 (94%) versus 1/17 (6%) (P < .0001); diffusion restriction: 1/17 (6%) versus 8/12 (67%) (P = .0009).

CONCLUSIONS

Younger age, diabetes insipidus, MR imaging characteristics of restricted diffusion, and vertical infundibular extension favor the diagnosis of germ cell tumors. Spheric shape without infundibular infiltration provides clues to papillary craniopharyngiomas, which originate from the pars tuberalis and are located outside the third ventricle. We suggest that suprasellar germ cell tumor is possibly an intraventricular lesion. Appropriate treatment planning can be initiated according to the diagnosis and anatomic location.

Early response to chemotherapy as an indicator for the management of germinoma-like tumors of the pineal and/or suprasellar regions

Recent advances in diagnostic imaging and experience with germinomas may allow for the differentiation of central nervous system germinomas from other tumors based on clinical information, without histological verification. We retrospectively analyzed clinically diagnosed germinoma-like tumors of the pineal and/or suprasellar regions. This was done to evaluate the efficacy of our strategy of defining germinoma-compatible tumors based on good responses to initial chemotherapy. The responses to chemotherapy and survival of 34 consecutive patients with germinoma-like tumors who underwent initial treatment from July 2001 to October 2010 were analyzed. The minimum apparent diffusion coefficient (minADC) value and proton magnetic resonance spectroscopy (MRS) were evaluated in recent patients. Twelve patients with histologically verified germinomas and 18 with germinoma-compatible tumors showed early logarithmic decreases in tumor volume in response to initial chemotherapy, typical low minADC values and typical MRS characteristics, including increased choline/creatine ratios, decreased N-acetylasparate/creatine ratios, and large lipid peaks. These patients had good progression-free survival. The other four patients, with histologically verified non-germinomas, showed no response to chemotherapy, and one patient with a pineoblastoma showed a similar minADC value and MRS characteristics to those of patients with germinomas. The response to initial chemotherapy can be used to distinguish germinoma-compatible tumors from non-germinoma in patients with germinoma-like tumors of the pineal and/or suprasellar regions. The evaluation of minADC and proton MRS are useful for distinguishing germinomas from other tumors. However, a subset of non-germinomas may show similar characteristics to germinomas. The benefit of bypassing unnecessary surgical intervention can be achieved, at least in Asian populations with a high incidence of germinomas.

Conventional and advanced MRI features of pediatric intracranial tumors: supratentorial tumors

OBJECTIVE. Our objective is to review the imaging characteristics and applications of conventional and advanced neuroimaging techniques of supratentorial intracranial masses in the pediatric population. Specifically, we review astrocytomas, oligodendrogliomas, primary neuroectodermal tumors, dysembryoplastic neuroepithelial tumors, gangliogliomas, arachnoid cysts, and choroid plexus and pineal region masses. CONCLUSION. Advanced imaging methods, such as MR spectroscopy, perfusion MRI, functional MRI, diffusion-tensor imaging, and tractography, help develop a more accurate differential diagnosis and aid in planning tumor treatment.