Intracranial germ cell tumors: detection of p53 gene mutations by single-strand conformation polymorphism analysis

Epigenetic Regulation in Primary CNS Tumors: An Opportunity to Bridge Old and New WHO Classifications

Originally approved in 1979, a specific grading classification for central nervous system (CNS) tumors was devised by the World Health Organization (WHO) in an effort to guide cancer treatment and better understand prognosis. These "blue books" have since undergone several iterations based on tumor location, advancements in histopathology, and most recently, diagnostic molecular pathology in its fifth edition. As new research methods have evolved to elucidate complex molecular mechanisms of tumorigenesis, a need to update and integrate these findings into the WHO grading scheme has become apparent. Epigenetic tools represent an area of burgeoning interest that encompasses all non-Mendelian inherited genetic features affecting gene expression, including but not limited to chromatin remodeling complexes, DNA methylation, and histone regulating enzymes. The SWItch/Sucrose non-fermenting (SWI/SNF) chromatin remodeling complex is the largest mammalian family of chromatin remodeling proteins and is estimated to be altered in 20-25% of all human malignancies; however, the ways in which it contributes to tumorigenesis are not fully understood. We recently discovered that CNS tumors with SWI/SNF mutations have revealed an oncogenic role for endogenous retroviruses (ERVs), remnants of exogenous retroviruses that integrated into the germline and are inherited like Mendelian genes, several of which retain open reading frames for proteins whose expression putatively contributes to tumor formation. Herein, we analyzed the latest WHO classification scheme for all CNS tumors with documented SWI/SNF mutations and/or aberrant ERV expression, and we summarize this information to highlight potential research opportunities that could be integrated into the grading scheme to better delineate diagnostic criteria and therapeutic targets.

Comparison on epidemiology, tumor location, histology, and prognosis of intracranial germ cell tumors between Mayo Clinic and Japanese consortium cohorts

OBJECTIVE

Central nervous system (CNS) germ cell tumors (GCTs) are rare malignant neoplasms that arise predominantly in adolescents and young adults. CNS GCTs demonstrate characteristic trends in national associations, with implications for both tumor incidence and genetics. Although the incidence of CNS GCTs is markedly higher in East Asia than Western countries, direct comparative analyses between these CNS GCT populations are limited.

METHODS

In Japan, to facilitate the genomic analyses of CNS GCTs, the Intracranial Germ Cell Tumor Genome Analysis Consortium was established in 2011, and more than 200 cases of GCTs are available for both tumor tissue and clinical data, which is organized by the National Cancer Center (NCC) Japan. At the Mayo Clinic, there have been 98 cases of intracranial GCTs treated by the Department of Neurologic Surgery since 1988. In this paper, the authors compared the epidemiology, clinical presentation including location and histology, and prognosis between cases treated in the US and Japan.

RESULTS

There was no significant difference in age and sex distributions between the databases. However, there was a significant difference in the tumor locations; specifically, the frequency of basal ganglia was higher in the NCC database compared with the Mayo Clinic (8.4% vs 0%, p = 0.008), and bifocal location (neurohypophysis and pineal gland) was higher at the Mayo Clinic than at the NCC (18.8% vs 5.8%, p = 0.002). There was no difference in histological subdivisions between the databases. There was no difference in progression-free survival (PFS) and overall survival (OS) of germinoma cases and OS of nongerminomatous GCT (NGGCT) cases treated with chemotherapy and radiation therapy covering whole ventricles. However, PFS of NGGCTs differed significantly, and was better in the NCC cohorts (p = 0.04).

CONCLUSIONS

There appears to be a differential distribution of GCTs by neuroanatomical location between major geographic and national groups. Further study is warranted to better characterize any underlying genomic, epigenetic, or environmental factors that may be driving the phenotypic differences.

A Case of Urachal Yolk Sac Tumor With Spontaneous Rupture in a Child

Tumors arising from urachus in children are exceedingly rare and sporadically reported in literature. Being a midline structure, the urachus may harbor neoplastic germ cell elements and can occasionally present as a case of acute abdomen. A 20-month-old toddler presented with spontaneous rupture of an urachal yolk sac tumor causing hemoperitoneum. He underwent resection, received platinum-based chemotherapy and presently remains well on follow-up. Despite its rarity, urachal germ cell tumors must be considered in a child with acute abdomen and tumor markers must be measured preemptively in such cases.

Molecular genetic analysis of a suprasellar immature teratoma : mutation of exon 4 p53 gene

We described an intracranial immature teratoma in a 13 year old Malay boy who presented with history of chronic headache and blurring of vision. Physical findings revealed bilateral papilloedema but no other localizing sign. A Magnetic Resonance Imaging of the brain revealed a suprasellar well defined lobulated midline heterogenous mass which was intraoperatively described as mainly solid tumour with multiple small cystic component filled with yellowish jelly like material. Histopathological finding confirmed the case as immature teratoma. Molecular genetic analysis of p53 and p27 genes revealed substitution of nucleotide G to C at location nucleotide 12139, exon 4 of gene p53. No alteration was detected at exon 5-6 and 8 of p53 gene and exon 1 and 2 of p27 gene. This is the first case report of an intracranial immature teratoma with genetic mutation occuring in a Malay boy.

Primary yolk sac tumor of the urachus

Pure yolk sac tumor is the most common malignant gonadal tumor of infants and toddlers. However, the majority of extragonadal germ cell tumors in the midline are either seminomas (germinomas) or teratomas, and pure yolk sac tumors account for only a small fraction of these lesions. To date, only 1 primary urachal pure yolk sac tumor has been reported in the literature. We describe another case, occurring in a 7-month-old male infant who presented with a rapidly enlarging intra-abdominal tumor with marked engorgement of the superficial venous plexus around the umbilicus. With periodic follow-up for 3 years following surgical extirpation of the tumor and adjuvant chemotherapy, this patient is still alive without evidence of disease. Notably, the glandular elements predominating in the frozen sections resulted in the initial misdiagnosis of the tumor as a urachal adenocarcinoma, although the entirely resected specimen revealed typical histologic patterns and Schiller-Duval bodies. Immunohistochemistry showed that the tumor cells were diffusely reactive to alpha-fetoprotein, alpha(1)-antitrypsin, and cytokeratin. Tumor cells were negative for p53 protein, but revealed overexpression for MDM2 protein. Flow cytometry demonstrated a diploid DNA content with S-phase being as high as 55.36%. This case emphasizes that pure yolk sac tumor can occur primarily in the remnant of the urachus in young children.

Molecular genetics of pineal region neoplasms

A large variety of mass lesions have been reported in the region of the pineal gland. Pineal parenchymal tumors and germ cell tumors (GCTs) are especially characteristic of this region. Despite their rarity, a number of excellent studies on the cytogenetics and molecular genetics of pineal parenchymal tumors and pineal region GCTs have been published. These studies draw attention to a number of distinct genomic regions recurrently involved in the various subtypes of malignancies of the pineal gland. Outcomes for tumors in this location vary widely between patients and among differing histologies. Development of novel therapies for patients with poor prognoses will depend on the acquisition of a more detailed understanding of the molecular basis associated with the etiopathogenesis of these neoplasms. We review the literature on cytogenetics, familial syndromes, animal models and molecular genetics of pineal region neoplasms.

Cytogenetic profile of primary pituitary germinoma

We present a case of a germinoma in the sellar region of a 10-year-old female patient who presented with a history of polydipsia, polyuria and visual disturbances. The tumor was resected and histologically analyzed. Interphase cytogenetics was performed using chromosome specific (peri)-centromeric DNA probes for all the somatic and X chromosomes on fresh frozen tissues. Fluorescent in situ cell hybridization demonstrated accumulated cytogenetic abnormalities involving significant alterations of chromosome 1, 4, 5/19 and 15. The child was treated postoperatively by radiation and now appears well with only minor neurological deficits. At 3-year follow-up no recurrent tumor mass could be demonstrated.

Comparative genomic hybridization in pineal germ cell tumors

Fifteen primary pineal germ cell tumors (8 germinomas, 4 mixed teratomas-germinomas, 2 immature teratomas, and 1 yolk sac tumor) and 2 recurrences of the yolk sac tumor were studied by comparative genomic hybridization (CGH). An average of 1.8 chromosomal changes per germinoma (0.5 gains vs 1.3 losses), 5.5 per mixed teratoma-germinoma (3.0 gains vs 2.5 losses), 3.5 per immature teratoma (2.0 gains vs 1.5 losses), and 2.0 in the yolk sac tumor (2 gains vs 0 losses) were found; the first recurrence showed 7 (4 gains vs 3 losses), the second 13 imbalances (8 gains vs 5 losses). The most frequent imbalances were gains on 12p (40%), 8q (27%), and 1q (20%) as well as losses on 13q (47%), 18q (33%), 9q and 11q (20% each). Among germinomas, the most common chromosomal changes were -13q and -18q (38% each), in mixed teratomas-germinomas +8q (100%), +12p (75%), -13q (75%) and -9q (50%). Seven high-level gains were identified: 5 in mixed teratomas-germinomas (+8q: 3 cases, + 12p: 2 cases), 1 each in a germinoma (+2p) and an immature teratoma (+12p). Minimal common regions of over- and underrepresentation were found on +8q11.22-21.1, +12p11.1-12.1, -9q32-qter, -11q23.2-qter, -13q32-qter and -18q22-qter. Our findings suggest, that imbalances in cerebral germ cell tumors affect the same chromosomes as among their extracerebral counterparts, albeit in a considerably lower frequency among cerebral germinomas where +12p does not seem to play a major role.

Astrocytoma and B-cell lymphoma development in a man with a p53 germline mutation

We report a case with a germline mutation of the p53 gene develpoing both a non-Hodgkin's lymphoma and an astrocytoma. The astrocytoma could be cured by two operations and combined chemotherapy but 33 months after the onset of the disease, he suffered from a diffuse, large cell centroblastic malignant lymphoma of B-cell lineage. In spite of clear rearranged fragments observed with IgH and c-MYC gene probes, we could not diagnose a Burkitt's lymphoma morphologically. The malignant lymphoma was chemoresistant and the patient died of multi-organ failure. He was confirmed to have a germline mutation of the p53 gene by analysis of c-DNA from peripheral lymphocytes and loss of heterozygosity (LOH) of p53 was evident in the lymphoma. The results were suggestive of the Li-Fraumeni syndrome (LFS), a rare autosomal dominantly inherited syndrome with a germline mutation of p53 gene and diverse malignancies, but this could not be confirmed in the present case. Alternatively, a de novo mutation could have been involved.

Immunohistochemical analysis of p53 and p21WAF1/Cip1 expression in primary intracranial germ cell tumors

Primary intracranial germ cell tumors (GCTs) comprise 3.1% of all brain tumors and 13.6% of those in patients younger than 15 years of age in Japan. They are classified into five basic histological types: germinoma, teratoma, choriocarcinoma, yolk sac tumor, and embryonal carcinoma; or into mixed tumor types when they consist of two or more components. Radiation therapy with or without chemotherapy has proven effective in the treatment of germinoma, whereas there is a poor prognosis for choriocarcinoma, yolk sac tumor, embryonal carcinoma, and mixed tumors having components of the group of malignant intracranial GCTs. The underlying mechanisms for such different responses to radio- and chemotherapies of intracranial GCTs remain unknown.

In this study, the authors analyzed the expression of p53 and p21WAF1/Cip1 proteins by immunohistochemical analysis in 35 intracranial GCTs. Expression of p53 protein was observed in 33 (94%) of 35 intracranial GCTs. Expression of p21WAF1/Cip1 was detected in seven (20%) of 35 intracranial GCTs. None of the 15 germinomas was immunoreactive for p21WAF1/Cip1 protein, whereas in a group of malignant intracranial GCTs, four (80%) of five cases showed immunoreactivity for p21WAF1/Cip1 protein. Analysis of the data suggests that overexpression of p21WAF1/Cip1 in intracranial GCTs may correlate with decreased sensitivity to radio- and chemotherapy and suggest a poor prognosis.