Genetic zygosity of mature ovarian teratomas, struma ovarii, and ovarian carcinoids

Molecular Biology of Pediatric and Adult Ovarian Germ Cell Tumors: A Review

Ovarian germ cell tumors (OGCTs) are rare in adults; indeed, they occur predominantly in children, adolescents, and young adults, and they account for approximately 11% of cancer diagnoses in these groups. Because OGCTs are rare tumors, our current understanding of them is sparse; this is because few studies have investigated the molecular basis of pediatric and adult cancers. Here, we review the etiopathogenesis of OGCTs in children and adults, and we address the molecular landscape of these tumors, including integrated genomic analysis, microRNAs, DNA methylation, the molecular implications of treatment resistance, and the development of in vitro and in vivo models. An elucidation of potential molecular alterations may provide a novel field for understanding the pathogenesis, tumorigenesis, diagnostic markers, and genetic peculiarity of the rarity and complexity of OGCTs.

Immature Teratoma: Diagnosis and Management-A Review of the Literature

An immature teratoma is a germinal malignant tumor composed of three germ cell layers, occurring more frequently in young women. It is the second most frequent among the malignant germinal tumors after dysgerminoma, and it is the only neoplasm with germ cells that are histologically graded. Even if we do not have a consensus regarding its therapeutical management, it has a good prognosis, with an excellent overall survival rate and good fertility preservation. More studies are needed regarding the necessity of adjuvant chemotherapy in pediatric oncology, and because of chemotherapy's long-term adverse effects, surveillance or a targeted treatment is preferred, but the main therapy is fertility-sparing surgery. Special attention should be given to the genetic mapping of the histological pieces for patient risk stratification due to its value in prognosis and future treatment.

The Association of Ovarian Teratoma and Anti-N-Methyl-D-Aspartate Receptor Encephalitis: An Updated Integrative Review

Ovarian teratomas are by far the most common ovarian germ cell tumor. Most teratomas are benign unless a somatic transformation occurs. The designation of teratoma refers to a neoplasm that differentiates toward somatic-type cell populations. Recent research shows a striking association between ovarian teratomas and anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis, a rare and understudied paraneoplastic neurological syndrome (PNS). Among teratomas, mature teratomas are thought to have a greater relevance with those neurological impairments. PNS is described as a neurologic deficit triggered by an underlying remote tumor, whereas anti-NMDAR encephalitis is characterized by a complex neuropsychiatric syndrome and the presence of autoantibodies in cerebral spinal fluid against the GluN1 subunit of the NMDAR. This review aims to summarize recent reports on the association between anti-NMDAR encephalitis and ovarian teratoma. In particular, the molecular pathway of pathogenesis and the updated mechanism and disease models would be discussed. We hope to provide an in-depth review of this issue and, therefore, to better understand its epidemiology, diagnostic approach, and treatment strategies.

Malignant struma ovarii with late recurrence harbouring high microsatellite instability

Struma ovarii (SO) is a rare ovarian teratoma containing abundant mature thyroid tissue. Malignant transformation is even less common and distant metastasis is documented in about 5%-10%. The time from diagnosis of primary SO to metastatic disease varies. As malignant SO is rare, there are no uniform diagnostic criteria or treatment guidelines. Management is usually extrapolated from that of thyroid malignancy. We report a patient who relapsed 12 years from the initial diagnosis and metastasised to the lungs 5 years after the first recurrence. Our patient was treated with total thyroidectomy followed by radioactive iodine, and retreated on progression in the lungs. The tumour harboured high microsatellite instability and treatment with programmed cell death protein 1 inhibitor was initiated. This case shows the long latency of SO with the rare phenomenon of metastasis. It also highlights the importance of molecular testing for rare cancers such as this.

Single nucleotide polymorphism array and cytogenetic analyses of ovarian teratomas in children

Teratomas are the most common tumors in the ovary during childhood. Previous studies suggested that they may be derived from germ cells at any developmental stage from premeiotic oogonia through meiotic oocytes to post-meiotic ova. The majority of mature teratomas reveal normal karyotypes and immature teratomas show higher frequency of chromosomal abnormalities. We analyzed fresh tissue samples from 25 primary ovarian teratomas and three extraovarian deposits using whole genome single nucleotide polymorphism (SNP) array and karyotype. SNP array detected five patterns of copy neutral loss of heterozygosity (CN-LOH): failure of meiosis I (type I) in 12 tumors, failure of meiosis II (type II) in six tumors, endoreduplication of a haploid ovum (type III) in two tumors, premeiotic error (type IV) in four tumors, and both meiotic I and meiotic II errors in one tumor (type V). Three tumors with type I error had a single chromosome showing meiotic II error, and two tumors with type II error had a single chromosome showing premature sister-chromatid separation in meiosis I. Lack of recombination in multiple chromosomes in meiosis I were common, chromosomes 17, 7, 8, 21, and 22 were most commonly involved. Abnormal karyotypes were observed in four teratomas including +3, del(3q), +7, +8, +12, and i(18q). The extraovarian deposits revealed the same CN-LOH pattern as the primary teratoma. In summary, SNP array reveals the origin of ovarian teratoma and we propose a new mechanism that consecutive meiotic I and II errors occur frequently in ovarian teratomas.

Methylation profiles of imprinted genes are distinct between mature ovarian teratoma, complete hydatidiform mole, and extragonadal mature teratoma

Mature ovarian teratoma is considered to be a parthenogenetic tumor that arises from a single oocyte/ovum. Conversely, complete hydatidiform mole (CHM) is androgenetic in origin: classic CHM arises from a single or two sperm. Since mature ovarian teratoma and CHM have only maternal and paternal genomes, respectively, their genome imprinting is theoretically reverse, but this has yet to be investigated. Genome imprinting in struma ovarii, a special form of mature teratoma, remains unclear. Although a mature teratoma can rarely arise in extragonadal sites, its genome imprinting, as well as cell origin, is poorly understood. One of the most important mechanisms of genome imprinting is DNA methylation. To investigate the methylation profile of imprinted genes, we performed methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA) of 21 imprinting control region (ICRs) of 9 imprinted genes/gene clusters in formalin-fixed, paraffin-embedded samples obtained from 12 mature ovarian teratomas, 6 struma ovarii, 10 CHMs, and 7 extragonadal (1 sacrococcygeal, 6 mediastinal) mature teratomas of females. In mature ovarian teratomas, ICRs of maternally and paternally imprinted genes showed high and low levels of methylation, respectively, and this pattern was almost reverse in CHMs. In CHMs, however, some ICRs showed aberrant methylation. The methylation profile of struma ovarii was comparable to that of mature ovarian teratomas, except for an adenomatous tumor. In extragonadal mature teratomas, the methylation pattern was somatic or irregular. In conclusion, mature ovarian teratomas/struma ovarii, CHMs, and extragonadal mature teratomas showed distinct methylation profiles of imprinted genes. Ovarian teratomas and CHMs are most likely to inherit their methylation profiles from their ancestral germ cells, although some aberrant methylation suggests a relaxation of imprinting in CHMs and a subset of struma ovarii. Extragonadal mature teratomas may carry a methylation profile of misplaced primordial germ cells or possibly somatic cells that have been reprogrammed in vivo.

Whole-Genome and Segmental Homozygosity Confirm Errors in Meiosis as Etiology of Struma Ovarii

Strumae ovarii are neoplasms composed of normal-appearing thyroid tissue that occur within the ovary and rarely spread to extraovarian sites. A unique case of struma ovarii with widespread dissemination detected 48 years after removal of a pelvic dermoid provided the opportunity to reexamine the molecular nature of this form of neoplasm. One tumor, from the heart, consisting of benign thyroid tissue was found to have whole-genome homozygosity. Another tumor from the right mandible composed of malignant-appearing thyroid tissue showed whole-genome homozygosity and a deletion of 7p, presumably the second hit that transformed it into a cancerous tumor. Specimens from 2 other cases of extraovarian struma confined to the abdomen and 8 of 9 cases of intraovarian struma showed genome-wide segmental homozygosity. These findings confirm errors in meiosis as the origin of struma ovarii. The histological and molecular findings further demonstrate that even when outside the ovary, strumae ovarii can behave nonaggressively until they receive a second hit, thereafter behaving like cancer.

Meiotic gene activation in somatic and germ cell tumours

Background

Germ cell tumours are uniquely associated with the gametogenic tissues of males and females. A feature of these cancers is that they can express genes that are normally tightly restricted to meiotic cells. This aberrant gene expression has been used as an indicator that these cancer cells are attempting a programmed germ line event, meiotic entry. However, work in non‐germ cell cancers has also indicated that meiotic genes can become aberrantly activated in a wide range of cancer types and indeed provide functions that serve as oncogenic drivers. Here, we review the activation of meiotic factors in cancers and explore commonalities between meiotic gene activation in germ cell and non‐germ cell cancers.

Objectives

The objectives of this review are to highlight key questions relating to meiotic gene activation in germ cell tumours and to offer possible interpretations as to the biological relevance in this unique cancer type.

Materials and Methods

PubMed and the GEPIA database were searched for papers in English and for cancer gene expression data, respectively.

Results

We provide a brief overview of meiotic progression, with a focus on the unique mechanisms of reductional chromosome segregation in meiosis I. We then offer detailed insight into the role of meiotic chromosome regulators in non‐germ cell cancers and extend this to provide an overview of how this might relate to germ cell tumours.

Conclusions

We propose that meiotic gene activation in germ cell tumours might not indicate an unscheduled attempt to enter a full meiotic programme. Rather, it might simply reflect either aberrant activation of a subset of meiotic genes, with little or no biological relevance, or aberrant activation of a subset of meiotic genes as positive tumour evolutionary/oncogenic drivers. These postulates provide the provocation for further studies in this emerging field.

Practical applications of DNA genotyping in diagnostic pathology

INTRODUCTION

Among various human tissue identity testing platforms, short tandem repeat (STR) genotyping has emerged as the most powerful and cost-effective method. Beyond forensic applications, tissue identity testing has become increasingly important in modern medical practice, in areas such as diagnostic pathology. Areas covered: A brief overview of various molecular/genetic techniques for identity testing is provided. This includes restriction fragment length polymorphism, single nucleotide polymorphism array and STR genotyping by multiplex PCR. Diagnostic applications of STR genotyping are covered in greater details: genotyping diagnosis of gestational trophoblastic disease, resolving tissue specimen mislabeling or histologic contaminant or 'floaters', bone marrow engraftment/chimerism analysis and interrogation of the primary source of malignancy in patients receiving organ donation. Four clinical cases are then presented to further illustrate these important clinical applications along with discussion of the interpretation, limitations, and pitfalls of STR genotyping. Expert commentary: STR genotyping is currently the most applicable method of identity testing and has extended its role well into the practice of diagnostic pathology with novel and powerful applications beyond forensics.