Medulloblastoma Primitive Neuroectodermal Tumor

PNETs of the CNS are a group of embryonal tumors that histologically comprise poorly differentiated neural epithelial cells. These tumors occur predominantly, though not exclusively, in childhood and constitute approximately 20-30% of all childhood brain tumors [1]. This group of tumors shares the biologic propensity of dissemination throughout the subarachnoid space, in addition to recurrence or progression at the primary site.

Tumors of this histology are most common in the posterior fossa and, in this location, are commonly called medulloblastomas (Fig. 28.1a). However, tumors that histologically appear identical to those found in the posterior fossa can occur in other locations throughout the CNS, where they are referred to as supra-tentorial PNETs, pineoblastomas in the pineal region and retinoblastomas in the eye [2]. While PNETs of the posterior fossa and of other sites share a common histologic appearance and a similar propensity for a pattern of metastases, the issue of whether these tumors share a common origin in biology remains quite controversial [2]. Recent studies examining the

Fig. 28.1. a Axial MRI (T1), showing moderately sized medulloblastoma. Typical of medulloblastomas, this tumor involves the roof of the fourth ventricle, without invading the floor. Also note the markedly enlarged temporal horns of the lateral ventricles. b Post-operative axial gadolinium-enhanced MRI (T1), showing resection of the fourth ventricular tumor, as well as resolution of hydrocephalus.

Fig. 28.1. a Axial MRI (T1), showing moderately sized medulloblastoma. Typical of medulloblastomas, this tumor involves the roof of the fourth ventricle, without invading the floor. Also note the markedly enlarged temporal horns of the lateral ventricles. b Post-operative axial gadolinium-enhanced MRI (T1), showing resection of the fourth ventricular tumor, as well as resolution of hydrocephalus.

Cure Your Yeast Infection For Good

Cure Your Yeast Infection For Good

The term vaginitis is one that is applied to any inflammation or infection of the vagina, and there are many different conditions that are categorized together under this ‘broad’ heading, including bacterial vaginosis, trichomoniasis and non-infectious vaginitis.

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