Radiologic features of primary intracranial ectopic germinomas

RATIONALE Germinomas are sensitive to radiation therapy and chemotherapy; therefore, correct imaging diagnosis is crucial for them. However, the imaging findings of germinomas originating from off-midline regions displayed different patterns from those originating from midline areas. PATIENT CONCERNS The objective of this study is to describe the radiologic features of primary ectopic germinoma. We reviewed the MR and CT findings of 12 patients with histologically proven off-midline ectopic germinomas with off-midline locations. INTERVENTIONS All of these patients underwent conventional MR images and 3 of them underwent diffusion images. Additional CT images were available in 3 patients. Analysis was focused on the shape and entity of tumors in images, signs of hemiatrophy, and the involvement of fibers in diffusion images. OUTCOMES Well-defined (8/12) and ill-defined margin masses (4/12) were identified according to the shape of the mass. Multicystic masses were seen in 11 of the 12 patients. The solid component of the tumors had a high density (3/3) with calcifications (2/3) on CT images, iso- to hypointensity in T2WI (11/12) and restricted diffusion on apparent diffusion coefficient (ADC) maps (3/3). Hemiatrophy was observed in 5 cases and progressive hemiatrophy was observed in 1 case. Other signs included mild peritumoral edema (10/12), and hydrocephalus (7/12). Additionally, infiltration of the corticospinal tract (CST) was identified on diffusion tensor imaging (DTI) (2/2). LESSONS The results indicate that multicysitic entities and hypointensities in solid components on T2WI and hemiatrophy are the imaging features of ectopic germinomas. DTI has potential for assessing CST involvement.