Embryonal tumor with abundant neuropil and true rosettes: an autopsy case-based update and review of the literature

Abstract

Introduction: Embryonal tumor with abundant neuropil and true rosettes (ETANTR) is a rare subtype of primitive neuroectodermal tumors first reported in 2000. It is rare among the group of embryonal central nervous system tumors with approximately 50 reported cases. ETANTR has been suggested to be a separate entity among this group of tumors.

Case report: Herein, we present only the second autopsy case of ETANTR, which occurred in a 17-month-old boy, and was located in the brainstem. The tumor was inoperable, and despite chemotherapy, the child died 3 months after initial hospitalization. A brain only autopsy was performed.

Discussion: Neuropathological and neuroimaging examinations suggest ETANTR grew by expansion rather than invasion distorting anatomical structures of the posterior fossa. We suggest that the characteristic histopathological picture of the tumor is the result of multifocal and dispersed germinative activity surrounded by mature neuropil-like areas.

Conclusion: ETANTR is a pediatric tumor occurring in children under 4 with a significantly poor prognosis with more cases and research required to characterize this rare embryonal tumor.

Fig. 1

a MRI, 3DFSPGRT1 sequence, sagittal plane. The tumor is localized in the brainstem and is extremely expanding and deforming its structure. Noteworthy is severe compression of the fourth ventricle, but evidently between the tumor and lumen of the fourth ventricle, there remains a thin, uninterrupted strip of brain tissue (arrow). b MRI, DGRET1 with contrast, axial plane. Contrast enhancement within the tumor is conspicuously insignificant. c MRI, frFSET2, coronal plane. The tumor appears as a very well delineated expansive process, with heterogeneous signal, containing some fluid-filled areas at the level of fourth ventricle and medial part of left cerebellar hemisphere, which has atrophied. The tumor molds and compresses the brainstem and obliterates the fourth ventricle. Supratentorially, there are features of hydrocephalus with transudate of CSF into surrounding brain tissue. d Macroscopic cross section of the tumor at the level of the cerebellum. Noteworthy is the very distinct border between the tumor and apparently untouched but evidently severely displaced and compressed cerebellar tissue. e Characteristic mixture of neuropil-like paucicellular zones with quite uniformly scattered cellular “densities” consisting of small undifferentiated cells. Both within densities and also directly within neuropil zones, one could discern rosettes which are quite characteristic for this tumor, H&E, objective magnification ×10. f A close-up view of rosettes. Some with empty core but delicately contoured with pinkish line, and some with homogenous featureless core (arrow), H&E, objective magnification ×40

Fig. 2

a The more cellular zones (asterisk), in contrary to neuropil background, are rather negative for synaptophysin, objective magnification ×20. b All rosettes were negative for synaptophysin. Apart from the rosettes, strongly synaptophysin-positive cells with prominent processes resembling astrocytes rather than neurons were noted, objective magnification x40. c Both rosettes and almost all cells within cellular “densities” are strongly immunopositive for vimentin, objective magnification ×40. d Rosettes are negative for S100. However, between the rosettes there are S-100 positive cells with marked processes, objective magnification ×20. e Some mature looking synaptophysin-positive neurons (arrowheads) are scattered within neuropil, objective magnification ×40. f Proliferating activity as evidenced by immunopositivity to Ki67 was marked within rosettes and also around vessels (not shown in this picture), objective magnification ×40