Pediatric diencephalic tumors: a constellation of entities and management modalities

Abstract

The diencephalon is a complex midline structure consisting of the hypothalamus, neurohypophysis, subthalamus, thalamus, epithalamus, and pineal body. Tumors arising from each of these diencephalic components differ significantly in terms of biology and prognosis. The aim of this comprehensive review is to describe the epidemiology, clinical symptoms, imaging, histology, and molecular markers in the context of the 2021 WHO classification of central nervous system neoplasms. We will also discuss the current management of each of these tumors.

Keywords: adenoma; craniopharyngioma; diencephalon; germ cell tumor; langerhans cell histiocytosis; pineoblastoma.

Figure 1

Obtained from a patient at St. Jude Children’s Research Hospital, Memphis, Tennessee. Axial pre-contrast T1-weighted (A) and post-contrast T1-weighted (B) images, demonstrating a complex mass centered in the left greater than right hypothalamus/optic chiasm, with extension into the left temporal lobe and enhancing solid components (arrow). (C) Axial T2-weighted sequence demonstrating a large cyst in the left temporal lobe (arrow). The histologic section (D) demonstrates a glial neoplasm with alternating loose and more compact architecture and low levels of mitotic activity. Many eosinophilic Rosenthal fibers are present in the background. Hyalinized vessels are typical findings.

Figure 2

Obtained from a patient at St. Jude Children’s Research Hospital, Memphis, Tennessee. Coronal non-contrast head CT (A) demonstrating a calcified solid suprasellar mass (arrow), with a large cystic component extending into the third ventricle and the inferior frontal lobe on the left. Sagittal T2-weighted (B) and post-contrast T1-weighted (C) images demonstrating enhancing solid components (arrow). The histologic section (D) demonstrates an epithelial neoplasm with numerous fragments of “wet keratin” and microcalcifications in the background. The adjacent brain parenchyma shows reactive gliosis. Many Rosenthal fibers are present. Such reactive brain tissue may masquerade as pilocytic astrocytoma.

Figure 3

Obtained from a patient at St. Jude Children’s Research Hospital, Memphis, Tennessee. Coronal pre-contrast T1-weighted (A) and post-contrast T1-weighted (B) imaging demonstrating a T1 isointense, heterogeneously enhancing sellar/suprasellar mass invading the left greater than right cavernous sinus and the left hypothalamus (arrow). The histologic section (C) shows sheets of tumor cells with “salt-and-pepper” chromatin in the nuclei. There is a loss of the usual lobular architecture and mixed cell population of the normal adenohypophysis. Apparent mitotic activity can be found in biologically aggressive tumors.

Figure 4

Obtained from a patient at St. Jude Children’s Research Hospital, Memphis, Tennessee. Sagittal T1 MRI images of pre- (A) and post- (B) contrast sequences demonstrating infundibular thickening >3 mm (arrow). Axial non-contrast CT of the temporal bone (C) demonstrating lytic-destructive change of the left mastoid air cells (arrow). (D) Axial CT image of the head, bone algorithm demonstrating a lytic lesion with a beveled edge in the left frontal calvarium (arrow). The histologic section (E) demonstrates numerous large and atypical tumor cells with abundant cytoplasm, prominent nucleoli, and irregular nuclear contour intermixed with many eosinophils and lymphocytes. The lesion can easily masquerade as an inflammatory or granulomatous process to inexperienced eyes.

Figure 5

Obtained from a patient at St. Jude Children’s Research Hospital, Memphis, Tennessee. Sagittal T1 pre- (A) and post- (B) contrast sequences demonstrating a T1 isointense, avidly enhancing sellar/suprasellar mass (arrows). The native pituitary tissue and infundibulum are not distinctly identified. The histologic section (C) demonstrates numerous discohesive large tumor cells accompanied by many lymphocytes, a characteristic finding in germinoma.

Figure 6

Obtained from a patient at St. Jude Children’s Research Hospital, Memphis, Tennessee. Sagittal FIESTA sequence demonstrating (A) a heterogeneous suprasellar mass with cystic components (arrow), (B) sagittal pre-contrast T1-weighted images demonstrating areas of intrinsic T1 hyperintensity compatible with blood products and/or proteinaceous debris (arrow), and (C) sagittal post-contrast T1-weighted images demonstrating an enhancing component in the anterior suprasellar cistern (arrow). (D) Axial non-contrast head CT demonstrating internal hemorrhage within the components to the left of midline (arrow), and (E) axial susceptibility-weighted imaging demonstrating a susceptibility artifact (arrow). The histologic section (F) shows embryonal carcinoma attached to the mesenchymal element of a teratoma. The large tumor cells in the embryonal carcinoma component have prominent nucleoli and basophilic cytoplasm.

Figure 7

Obtained from a patient at St. Jude Children’s Research Hospital, Memphis, Tennessee. Axial T2 sequence (A) demonstrating a T2 hyperintense, circumscribed mass involving the left thalamus without significant mass effect. Axial pre-contrast T1-weighted (B) and post-contrast T1-weighted (C) images demonstrate a T1 hypointense, avidly enhancing mass. The histologic section (D) shows a piloid glial neoplasm with low levels of mild activity. Many eosinophilic Rosenthal fibers are present in the background. Prominent endothelial cells are a common finding in pilocytic astrocytomas.

Figure 8

Obtained from a patient at St. Jude Children’s Research Hospital, Memphis, Tennessee. Axial FLAIR image (A) demonstrating a T2/FLAIR hyperintense infiltrative mass involving bilateral thalami with mass effect on the third ventricle and severe obstructive hydrocephalus. Axial diffusion-weighted (B) and apparent diffusion-coefficient maps (C) demonstrate no restricted diffusion. The histologic section (D) shows an infiltrative neoplasm with hyperchromatic nuclei and moderate nuclear pleomorphism. There are two large entrapped neurons.

Figure 9

Obtained from a patient at St. Jude Children's Research Hospital, Memphis, Tennessee. (A) Axial diffusion-weighted imaging and (B) apparent diffusion coefficient map demonstrating a hypercellular pineal region mass causing obstructive hydrocephalus. (C) Axial pre-contrast and (D) post-contrast T1 images demonstrating avid enhancement within the mass. (E) The histologic section demonstrates a hypercellular embryonal tumor with readily apparent mitotic activity. The tumor cells show nuclear hyperchromasia and an inconspicuous amount of cytoplasm.