CT and MRI of Skull Base Lesions by Igor Pronin & Valery Kornienko

Author:Igor Pronin & Valery Kornienko
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

15.7 Germinomas

Germinoma is one of the most frequent tumors of the pineal region, and only in 20% of cases they are found in the suprasellar cistern and much less frequently in the pituitary fossa. Suprasellar germinomas may be primary and originate from the suprasellar cistern, or they may be metastases from the pineal region germinomas. Germinomas consist of large polygonal embryonic cells, accumulations of lymphocytes and thick connective tissue stroma. The suprasellar germinomas are nonencapsulated tumors with infiltrative growth; they may embed metastases into the walls of the lateral ventricles and the basal cisterns.

Germinomas are tumors of children and young adults (5–30 years). They are manifested by endocrinological dysfunction such as diabetes insipidus or panhypopituitarism. Such manifestation confirms that the tumor involves the walls of the third ventricle. Defects of visual fields and optic nerve atrophy are usual. If the CSF pathways are blocked hydrocephalus occurs. Oculomotor signs may develop if a tumor grows into the parasellar space. There is a notion of occult neurohypophyseal germinomas in literature (Kato et al. 1998). In such cases, diabetes insipidus is not accompanied by any lesion in the optic chiasm and sellar area, and thickening of the stalk without a normal MR signal from the posterior pituitary is detected. A decrease in blood growth hormone levels or an elevated in blood human chorionic gonadotropin levels can be found.

Imaging

On CT without CE, germinomas are hyperdense and homogenously enhanced (Fig. 15.88). Calcifications are not usual for these tumors. Primary germinoma of the pineal region may be identified. The described characteristics are similar to those of lymphoma, differences can include age, clinical history and presence of a tumor in the pineal region.

Fig. 15.88Germinoma of the pineal region with dissemination into the suprasellar region and lateral ventricles. CE CT scans (a–c) show multiple foci of the contrast enhancement (arrows)—tumor in pineal region and metastases

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