Case Study 51

Jennifer Picarsic, M.D.

PGY-4 Resident

Question 1

Received in consultation are slides from a 5 month old girl with year history of intra-uterine hydrocephalus, large head at birth and left zygomatic mass Describe the radiographic appearance.

Head ultrasound at birth Head ultrasound at 1 month

MRI: T1 Coronal without contrast

MRI: Horizontal with contrast CT- Zygomatic mass

Head ultrasound at birth Dilated lateral ventricles Head ultrasound at 1 month Increased size lateral ventricles 

Head Ultrasound- Prominent hydrocephalous, 2 intraventricular masses.

3.0 cm 5.4 cm w/o C: Intraventricular mass centered at level of 4th ventricle, extends into 3rd; and measures 5.4 x 4.3 x 3.6 cm. Cerebellar tonsillar displacement downward filling the foramen magnum.

Second intraventricular mass is in lateral ventricle near foramen of Monroe, measuring 3 x 3 x 2.3 cm and is likely obstructing at this point, given the marked enlargement of the left lateral ventricle; with slit like right lateral ventricle 2/2 to mass effect. Third mass: left temporal lobe, with soft tissue extention.

w/C CT- Zygomatic mass Mild heterogeneous enhancement on post contrast images.

T2 (not shown) demonstrated increased signal intensity around the occipital horn of the left lateral ventricle —suggesting transepedymal flow

CT imaging shows of a left temporal mass lesion with bone and soft tissue component

with soft tissue extension as well as extension through calvarium. measuring, 2.5 cm

Question 2

What would be your radiographic differential diagnosis in this 5 month old child?

Answer

 A high grade lesion would be highest on the differential given the temporal mass eroding through calvarium and extending into soft tissue. There is a multifocal tumor with possible intraventricular spread, with primary involvement of the posterior fossa and obstructive hydrocephalus.

 PNET/Medulloblastoma with bony metastasis to left temporal region (decreased intensity on T1)  Atypical teratoid/rhabdoid tumor  Choroid plexus carcinoma (should have hyperintense, contrast enhancing lesions)  Ependymoma; ?Other high grade gliomas

Question 3

Describe the microscopic findings in a representative H&E sections of the subcutaneous temporal area tumor.

Part 1: Click

here

to view slide of Zygomatic mass that was biopsied Part 2: Click

here

to view slide from tissue came out with the needle of decompression of hydrocephalus

Answer

Part 1: Sheets of malignant appearing cells with a jumbled architecture, no real pattern, and no definite rosette formation. The cells have moderate eosinophilic cytoplasm with an occasional cell showing a more pink eccentrically placed cytoplasm, leaving a suggestion for rhabdoid morphology. The nuclei are pleomorphic with anaplasia, very prominent large nucleoli and irregular nuclear contours. Mitotic figures are abundant and occasional atypical mitoses are present. There are small areas of necrosis, apoptotic bodies, and a mild lymphocytic infiltrate. Part 2: Tissue that came out with the needle for decompression of hydrocephalus sampled normal choroid plexus. There was a very minute fragment of malignant appearing cells of to one edge. It was felt that the intraventricular masses represent the same malignancy as part 1, but were just were not specifically sampled.

Question 4

What immunohistochemical stains would help you in making your diagnosis?

Answer (IHC)

Atypical teratoid/rhabdoid tumor

Epithelial, neuronal, and mesenchymal markers should all be positive — EMA, CAM5.2, GFAP, Synaptophysin, NF, vimentin, SMA, myogenin

Medulloblastoma/supratentorial P-NET

Synaptophysin, NSE, GFAP, vimentin, S100 —

Medullomyoblastoma-myoglobulin, desmin positivity

Choroid Plexus Carcinoma

EMA, vimentin, cytokeratin, GFAP, p53, transthyretin, potassium channel Kir7.1 (mbr)

Ependymoma (anaplastic)

EMA (dot like), GFAP

Lymphoma (large cell or blastic)

LCA, CD3, CD20, PAX5, Tdt

synaptophysin

GFAP

SMA

Myogenin

CAM 5.2

EMA

Ki-67- 50%

IHC Stains

Synaptophysin - Rare tumor cells show cytoplasmic immunoreactivity GFAP- Tumor is negative Smooth muscle actin - Patchy light to moderate staining Myogenin - Scattered positive cells Desmin (not shown) - Tumor is negative CAM 5.2 – Patchy tumor positive staining EMA – Patchy tumor positive staining LCA (not shown) - Positive mostly in small infiltrating lymphocytes CD3 (not shown) - Positive mostly in small infiltrating lymphocytes CD20 (not shown) - Negative PAX5 (not shown) - Negative CD79a (not shown) - Rare positive cells; most of tumor shows equivocal light cytoplasmic blush Tdt (not shown) - Negative Ki67 - Tumor proliferative index is 50%.

Question 5

What additional IHC and molecular tests would help differentiate the two embryonal tumors?

INI-1 tumor negative; positive internal control

Transthyretin – nonspecific stain of serum Positive in Choroid plexus Carcinomas

Answer

 INI-1/ BAF47 -Tumor cells are negative; positive internal controls with endothelial cells/lymphocytes positive  Normally expressed in normal tissue without mutation/deletion  The loss kidney. The relative specificity is declining as more tumors show loss of INI-1 of nuclear staining is found in AT/RT, as well as RT of the  Molecular  AT/RT – monosomy deletion/mutations of 22p11.2 ( deletion (20%)

INI1/hSNF5

) gene (75%) (exons 5 and 9 hot spots) or less frequently a homozygous  May be a part of the rhabdoid tumor predisposition syndrome  Medulloblastoma survival) – nonspecific, +/- MYC/MYCN oncogene amplification (worst survival), also gains in 6q, 17q, and 6q loss (best

What is your final diagnosis

FINAL

 Part 1: SUBCUTANEOUS TUMOR, EXCISION: ATYPICAL TERATOID/RHABDOID TUMOR, WHO GRADE 4.

 Part 2: INTRAVENTRICULAR TUMOR, BIOPSY CHOROID PLEXUS WITH MINUTE FRAGMENT OF ATYPICAL TERATOID/RHABDOID TUMOR



Loss of INI-1

The complete loss of INI-1/BAF47 protein is thought to be specific finding for Atypical Teratoid / Rhabdoid Tumors of the CNS and kidney, which was recognized to have biallelic deletion/mutations at the 22q11.2 locus of the INI-1 gene (also known as

SMARCB1

,

hSNF5

, or

BAF47)

 Homozygous deletion or heterozygous deletion with a “second-hit” mutation of this tumor suppressor gene  The gene is important in the SWItch/Sucrose(SNF) ATP-dependent chromatin remodeling complex  Chromatin restricts the access to transcription factor DNA by tightly bound histones and other proteins  Protein groups such as the polycomb and trithorax protein groups act to remodel chromatin, thus altering the accessibility of DNA to factors required for gene transcription  The SWI/SNF complex controlled by the INI-1 gene allows chromatin remodeling for transcriptional regulation of specific genes to ensure correct cell identity during development and differentiation.

Loss of INI-1 insights into histogenesis

 Recently in renal rhabdoid tumors, neuronal and neural crest development genes are differentially down-regulated (

PTN, DOCK4,PTPRK, SPOCK1

), as compared to other pediatric renal tumors  The histogenesis is now thought to be an early progenitor cell at a critical developmental window in which loss of

INI-1

leads to arrest or repression of normal neural development, dysregulation of the thithorax/polycomb groups, and silencing of cell cycle dependent kinase inhibitors to allow uncontrolled growth  This may help explain why these tumors shows lineage of neuronal, epithelial, and mesenchymal origins.

 

Not as specific as we thought

While the complete loss of INI-1 was thought to be a defining genetic feature of the AT/RT, we are now seeing that it is not as specific as once thought Other tumors now show loss of INI-1 by IHC, without the classic histologic rhabdoid features of AT/RT, including cases with the diagnosis of Medulloblastoma/PNET, with molecular confirmation of 22q11.2 loss.

1  Previously diagnosed choroid plexus carcinomas have been re-classified as AT/RT based on loss of INI-1 staining, though there is still some controversy around this topic.

2  Rhabdoid glioblastomas have demonstrated both areas of complete INI-1 loss and other areas with INI-1 retention, compared to epithelioid glioblastomas which complete retention.

3  A newly proposed neuroectodermal tumor called cribriform neuroepithelial tumor (CRINET), was described in 2 children with contrast enhancing tumors of the 3 22q11.2 locus.

4 rd /4 showed loss of the INI-1 protein, with one demonstrating a stop codon mutation in th ventricles that had cribriform strands and trabeculae, without rhabdoid features but There was a lower proliferation index and these children are alive after 5 years.  Furthermore, syndromic schwannomatosis, including familial schwannomatosis, sporadic schwannomatosis and those in NF2 schawannomas show a heterogenous/mosaic pattern of INI-1 loss (ie. Mixture of cells both with loss of INI-1 adjacent to others with retention).

5

References

1.

Haberler et al.

Am J Surg Pathol

. 2006. Nov;30(11):1462 8.

2.

Judkins, Hamilton et al.

J Neuropathol Exp Neurol

. 2005 May;64(5):391-7. 3.

Kleinschmidt-DeMasters et al.

Am J Surg Pathol

. 2010 Mar;34(3):341-54. 4.

Hasselblatt et al.

J Neuropathol Exp Neurol.

2009;68(12):1249-1255.

5.

Patil et al.

Brain Pathol

. 2008 Oct;18(4):517-9.