Embryonal Tumors of the Central Nervous System: From the Radiologic Pathology Archives

Abstract

Embryonal tumors of the central nervous system (CNS) are highly malignant undifferentiated or poorly differentiated tumors of neuroepithelial origin and have been defined as a category in the World Health Organization (WHO) classification since the first edition of the "Blue Book" in 1979. This category has evolved over time to reflect our ever-improving understanding of tumor biology and behavior. With the most recent update in 2016, many previous histologic diagnoses incorporate molecular parameters for the first time (genetically defined entities). While medulloblastoma and atypical teratoid/rhabdoid tumor are familiar carryovers from the 2007 CNS WHO classification, there are major changes to the embryonal tumor category: for example, elimination of the term CNS primitive neuroectodermal tumor and addition of a new genetically defined entity, embryonal tumor with multilayered rosettes, C19MC-altered. The purpose of this article is to discuss both the radiologic-pathologic features of CNS embryonal tumors and the new molecularly defined types/subtypes that will become the standard classification/terminology for future diagnoses and tumor research.

Hemorrhagic Suprasellar Central Nervous System Embryonal Tumor in an Adult: Uncommon Features of an Extremely Rare Neoplasm

“…41 Radiologic patterns of supratentorial PNETs vary considerably and preoperative radiologic diagnosis may be difficult due to nonspecific CT and MRI characteristics. 42 At basal CT scan, these tumors are heterogeneous iso-to hypodense lesions with focal internal calcifications, necrosis, and cyst degeneration. The diagnosis of PNET should be considered at MR neuroimaging for lesions showing iso-to hyperintense T2-sequence signal and diffusion restriction on DWI/ADC maps, which are radiologic findings suggestive of increased cellularity and high nuclear-to-cytoplasmic ratio.…”

Multifocal recurrence of medulloblastoma: a long follow-up case study

“…11 HE staining of the mass further limited the differential of the tumor to be of small round blue cells with a high proliferation index in the Ki-67 staining, which is consistent with medulloblastoma. 10,12 The presence of Homer Wright rosette is pathognomonic for medulloblastoma in the posterior fossa tumor but can also be found in other supratentorial tumors, such as primitive neuroectodermal tumor and pineoblastoma. 13 For the temporal lobe mass of the presented case, the presence of rosette formation when combined with other pathological information, such as densely packed small round blue cell tumor with areas distributed in a ribboning pattern in HE staining, is highly suggestive of classic variant medulloblastoma.…”

“…13 For the temporal lobe mass of the presented case, the presence of rosette formation when combined with other pathological information, such as densely packed small round blue cell tumor with areas distributed in a ribboning pattern in HE staining, is highly suggestive of classic variant medulloblastoma. 12,13 β-catenin staining was not performed to exclude other possible diagnoses but is useful in determining the medulloblastoma molecular subgroup; a negative result showed the tumor is non-wingless (WNT) activated. 12 In the presented case, final MR imaging of the mass did not resemble typical medulloblastoma or its leptomeningeal metastasis.…”

“…12,13 β-catenin staining was not performed to exclude other possible diagnoses but is useful in determining the medulloblastoma molecular subgroup; a negative result showed the tumor is non-wingless (WNT) activated. 12 In the presented case, final MR imaging of the mass did not resemble typical medulloblastoma or its leptomeningeal metastasis. Although the patient's initial diagnosis of medulloblastoma could be mainly considered through the mass characteristics on the cerebellar vermis, the final MR presentation of the patient strongly showed its characteristic as an intra-axial mass of the temporal lobe without any clear trace of its leptomeningeal dissemination.…”

Imaging of brain tumors in children: the basics—a narrative review

“…Ultimately, AT/RT is a genetic/molecular diagnosis, defined in 98% of cases by the deletion in chromosome 22 and loss of SMARCB1/INI1 expression in cytogenetic analysis of the tissue which also differentiate them from medulloblastomas (91,98).…”