Germinoma pathophysiology
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Simrat Sarai, M.D. [2]
Overview
On gross pathology, smooth and bosselated external surface, and soft, fleshy and either cream-colored, gray, pink or tan interior are characteristic findings of germinoma. On microscopic histopathological analysis, uniform cells that resemble primordial germ cells, consisting of large, round cells with vesicular nuclei and clear or finely granular cytoplasm that is eosinophilic are characteristic findings of germinoma. Genes involved in the pathogenesis of germinoma include the chromosomal imbalance comprises gains of 1p, 8p, and 12q and losses of 13q and 18q. duplication of the short arm of chromosome 12, loss of 1p and 6q and alterations in sex chromosomes in children, alterations of the p14 gene, mutations of the c-kit gene, aberrations of CCND2 (12P13), and RB1, and and gain-of-function mutations of KIT. The progression to germinoma usually involves the mutations of the KIT/RAS signalling or AKT1/mtor pathways and cyclin/CDK-RB-E2F pathway if CCND2 (12P13) and RB1 genes are aberrated.
Pathophysiology
Pineal lesions occur more commonly than suprasellar lesions, at a ratio of 2:1. The location of the tumor that compromises total percentage of CNS germ cell tumors is shown below in a tabular form:[1]
| Location of the tumor | % of CNS GCT |
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The relationship of the gender with location of the CNS germ cell tumors is shown below in a tabular form:[2]
| Sex | Location of the tumor |
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Gross pathology
On gross examination, the external surface is smooth and bosselated (knobby), and the interior is soft, fleshy and either cream-coloured, gray, pink or tan.[3]
Microscopic pathology
Microscopic examination typically reveals uniform cells that resemble primordial germ cells. Typically, the stroma contains lymphocytes and about 20% of patients have sarcoid-like granulomas. The tumor is uniform in appearance, consisting of large, round cells with vesicular nuclei and clear or finely granular cytoplasm that is eosinophilic. Pure germinomas are composed of large polygonal undifferentiated cells with abundant cytoplasm arranged in nests separated by bands of connective tissue. The histologic appearance of Nongerminomatous germ cell tumors (NGGCTs) varies depending upon the specific cell types present.[3]
Pathogenesis
- Central nervous cell germ cell tumors (GCTs) are believed to arise from nests of embryonic cells arrested during their migration in fetal development in the midline structures. As a result, CNS GCTs are found in midline sites, especially in the suprasellar and pineal gland regions.
- The germ cell theory has postulated that these tumors arise from primordial germ cells that have migrated aberrantly during embryonic development and subsequently undergone malignant transformation. However, the embryonic cell theory suggests that GCTs arise from a mismigrational pluripotent embryonic cell. It is postulated that pure germinomas arise from germ cells whereas mixed NGGCTs are a result of misfolding and misplacement of embryonic cells into the lateral mesoderm, causing these cells to become entrapped in different areas of the brain.
- Intracranial GCTs express germ cell–specific proteins comprising NY-ESO-1, MAGE-A4, and TSPY, which are associated with embryonic stem cell pluripotency, which indicate that GCTs may originate from primordial germ cells.[4][5][6][7]
Genetics
- In adult-onset extragonadal germinomas, the most common abnormality is duplication of the short arm of chromosome 12.
- Cytogenetic abnormalities in children include loss of 1p and 6q, alterations in sex chromosomes, and abnormalities in 12p. In a study involving children, a subset of patients with pineal tumors demonstrated a gain of chromosomal material at 12p.
- In majority of cases, the most common chromosomal imbalance comprises gains of 1p, 8p, and 12q and losses of 13q and 18q.
- The most frequent genotype abnormality is XXY, similar to that in Klinefelter syndrome. Individuals with Klinefelter syndrome are prone to develop intracranial GCTs, as are those with neurofibromatosis, type 1 and Down syndrome.
- Gene p14 plays an important role in the development of intracranial germ cell tumors as frequent alterations of the p14 gene have been detected, especially in intracranial pure germinomas.
- In approximately 23-25% of intracranial germinomas, mutations of the c-kit gene have been found. C-myc and N-myc amplifications were seen in a minority of tumors. Genomic analysis of GCTs has revealed distinct mRNA and miRNA profiles which may be correlated with clinical outcome, histological differentiation, and may serve as novel therapeutic targets in future.[20]
- Frequent aberrations of CCND2 (12P13), and RB1 has indicated that there might be possibility of cyclin/CDK-RB-E2F pathway involvement in the pathogenesis of intracranial germ cell tumors. Gains in the transcriptional regulator PRDM14 have also been implicated in the pathogenesis of germ cell tumors. A recent study of 62 patients with intracranial GCT has shown that more than 50% had mutations of the KIT/RAS signalling or AKT1/mtor pathways.[8][9][10][11][12][13][14][15][16][12][13]
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Histopathology specimen of a germinoma located on the floor of the IIIrd ventricle in the brain - HE stain low magnification
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Histopathology specimen of a germinoma located on the floor of the IIIrd ventricle in the brain -HE stain intermediate magnification
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Histopathology specimen of a germinoma located on the floor of the IIIrd ventricle in the brain - HE stain very high magnification
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Histopathology specimen of a germinoma located on the floor of the IIIrd ventricle in the brain OCT 3/4
References
- ↑ Germ cell tumors. Radiopedia(2015) http://radiopaedia.org/articles/central-nervous-system-germinoma Accessed on January 25, 2016
- ↑ Villano JL, Propp JM, Porter KR, Stewart AK, Valyi-Nagy T, Li X; et al. (2008). "Malignant pineal germ-cell tumors: an analysis of cases from three tumor registries". Neuro Oncol. 10 (2): 121–30. doi:10.1215/15228517-2007-054. PMC 2613814. PMID 18287340.
- ↑ 3.0 3.1 germinoma. Wikipedia(2015) https://en.wikipedia.org/wiki/Germinoma Accessed on January 26, 2016
- ↑ Packer RJ, Cohen BH, Cooney K, Coney K (2000). "Intracranial germ cell tumors". Oncologist. 5 (4): 312–20. PMID 10964999.
- ↑ Teilum, Gunnar. Special tumors of ovary and testis and related extragonadal lesions : comparative pathology and histological identification. Copenhagen Philadelphia: Munksgaard J.B. Lippincott, 1976. Print.
- ↑ Nomura K (2001). "Epidemiology of germ cell tumors in Asia of pineal region tumor". J Neurooncol. 54 (3): 211–7. PMID 11767288.
- ↑ Sano K, Matsutani M, Seto T (1989). "So-called intracranial germ cell tumours: personal experiences and a theory of their pathogenesis". Neurol Res. 11 (2): 118–26. PMID 2569683.
- ↑ Rickert CH, Simon R, Bergmann M, Dockhorn-Dworniczak B, Paulus W (2000). "Comparative genomic hybridization in pineal germ cell tumors". J Neuropathol Exp Neurol. 59 (9): 815–21. PMID 11005262.
- ↑ Schneider DT, Zahn S, Sievers S, Alemazkour K, Reifenberger G, Wiestler OD; et al. (2006). "Molecular genetic analysis of central nervous system germ cell tumors with comparative genomic hybridization". Mod Pathol. 19 (6): 864–73. doi:10.1038/modpathol.3800607. PMID 16607373.
- ↑ Palmer RD, Foster NA, Vowler SL, Roberts I, Thornton CM, Hale JP; et al. (2007). "Malignant germ cell tumours of childhood: new associations of genomic imbalance". Br J Cancer. 96 (4): 667–76. doi:10.1038/sj.bjc.6603602. PMC 2360055. PMID 17285132.
- ↑ Sato K, Takeuchi H, Kubota T (2009). "Pathology of intracranial germ cell tumors". Prog Neurol Surg. 23: 59–75. doi:10.1159/000210053. PMID 19329861.
- ↑ 12.0 12.1 Kamakura Y, Hasegawa M, Minamoto T, Yamashita J, Fujisawa H (2006). "C-kit gene mutation: common and widely distributed in intracranial germinomas". J Neurosurg. 104 (3 Suppl): 173–80. doi:10.3171/ped.2006.104.3.173. PMID 16572634.
- ↑ 13.0 13.1 Sakuma Y, Sakurai S, Oguni S, Satoh M, Hironaka M, Saito K (2004). "c-kit gene mutations in intracranial germinomas". Cancer Sci. 95 (9): 716–20. PMID 15471556.
- ↑ Wang HW, Wu YH, Hsieh JY, Liang ML, Chao ME, Liu DJ; et al. (2010). "Pediatric primary central nervous system germ cell tumors of different prognosis groups show characteristic miRNome traits and chromosome copy number variations". BMC Genomics. 11: 132. doi:10.1186/1471-2164-11-132. PMC 2837036. PMID 20178649.
- ↑ Terashima K, Yu A, Chow WY, Hsu WC, Chen P, Wong S; et al. (2014). "Genome-wide analysis of DNA copy number alterations and loss of heterozygosity in intracranial germ cell tumors". Pediatr Blood Cancer. 61 (4): 593–600. doi:10.1002/pbc.24833. PMID 24249158.
- ↑ Wang L, Yamaguchi S, Burstein MD, Terashima K, Chang K, Ng HK; et al. (2014). "Novel somatic and germline mutations in intracranial germ cell tumours". Nature. 511 (7508): 241–5. doi:10.1038/nature13296. PMC 4532372. PMID 24896186.