Microdissection-based analysis of mature ovarian teratoma

Role of gene sequencing in classifying struma ovarii: BRAF p.G469A mutation and TERT promoter alterations favour malignant struma ovarii

AIMS

Struma ovarii (SO) are rare, accounting for 0.3-1% of ovarian tumours, and include benign and malignant lesions. In most cases, histology is not predictive of clinical outcome and prognosis. The prognosis of histologically malignant thyroid-type carcinomas can indeed be excellent, while SO, composed of normal thyroid tissue, can recur and are designated highly differentiated follicular carcinoma of the ovary. Clearer diagnostic criteria are therefore required.

METHODS AND RESULTS

We retrospectively studied 31 SO using DNA and RNA sequencing with pan-cancer gene panels, including eight biologically malignant SO (BMSO) defined based on ovarian serosal or extra-ovarian dissemination at presentation or during follow-up, 10 stage IA histologically malignant SO (HMSO) with thyroid-type carcinoma morphology and 13 biologically and histologically benign SO (BSO), with none of the above-mentioned characteristics. Molecular alterations were observed in 87.5% of BMSO, 70% of HMSO and 7.7% of BSO (P < 0.001). All patients with a peritoneal dissemination at presentation or during follow-up had at least one gene alteration. BRAF mutations (44.5%) were only observed in malignant forms (HMSO and BMSO) and TERT promoter alterations (25%) only in cases of BMSO. The BRAF p.G469A mutation, which is extremely rare in thyroid carcinomas, was the molecular alteration most frequently associated with malignant SO (28.5%).

CONCLUSION

Our results highlight the clinical utility of molecular sequencing in SO, based on this limited number of cases. However, as malignant SO evolve slowly, more extensive molecular studies in SO with more than 10 years' follow-up are required to draw any conclusions on the prognostic value of the associated gene alterations.

Mature Cystic Teratoma: An Integrated Review

Ovarian dermoid cysts, also called mature cystic teratomas (MCTs), account for 69% of ovarian germ cell tumors in young women. The tumors are formed by tissues derived from three germ layers, and sebaceous materials are most commonly seen. The origin of MCTs is widely considered to be the germ cell origin, which completes meiosis I. The clinical symptoms vary widely, but 20% of tumors could be asymptomatic. The diagnosis of MCTs is usually made without difficulty by ultrasound and confirmed by histopathology post-operatively. The imaging findings have a high diagnostic value. The typical characteristics present in the sonographic images, including a dermoid plug or Rokitansky nodule, are considered strong evidence for a teratoma. Although the malignant transformation of MCTs is rare, it can occur in some cases, especially in women of advanced age. The treatment of MCTs depends on the risk of malignancy, the age of the patient, and the patient's fertility reserve requirement. In this article, we review the epidemiology, clinical symptoms, diagnosis criteria, cellular origin, and treatment of mature cystic teratomas.

Cervical Cystic Teratoma: An Unusual Cause of Airway Obstruction in the Pediatric Population

Cystic teratoma is a germ cell tumor, which usually involves the gonads. However, it can be located occasionally in other organs. The most common extragonadal sites for germ cell tumors include midline structures such as the retroperitoneum, mediastinum, pineal body, and supra-sellar space. Here, we describe a case of a patient who presented with a cystic teratoma involving the anterior aspect of the neck. The chief complaints of the patient consisted of a large swelling in front of the neck, difficulty in breathing, and frequent regurgitation of milk during feeding. Initially, a diagnosis of cystic hygroma was instituted for which the patient underwent sclerotherapy utilizing bleomycin. However, no improvement was observed in the patient's condition. A detailed evaluation was planned, starting with a CT scan of the head and neck that suggested cystic teratoma as the likely etiology. Surgical excision of the mass was performed, and an excisional biopsy for histopathological examination was taken. A final diagnosis of cervical cystic teratoma was established based on the histopathological findings. The purpose of reporting this case is to raise awareness among fellow healthcare professionals that cystic teratoma can also present with a large swelling in the anterior neck with obstructive features.

Prostatic tissue: an unexpected finding in a mature ovarian teratoma : Case report and systematic literature review

PURPOSE

Prostatic tissue in an ovarian teratoma is an unusual finding, whose initiation in a 46, XX karyotype tissue is yet to be clarified. We present a case from our files and review the literature for this intriguing finding.

METHODS

Unstained histology sections of the ovarian teratoma containing prostatic tissue were evaluated using immunohistochemistry for PSA and androgen receptor.

RESULTS

Both PSA and androgen receptor immunostainings were positive in the prostatic tissue. From the literature review, it appears that most of the patients (74%) with similar findings were either pregnant or experiencing a miscarriage, menopausal or infertile at presentation, showing that an imbalanced hormone status is frequently associated with the presence of male structures in ovarian teratomas.

Methylation profile of imprinted genes provides evidence for teratomatous origin of a subset of mucinous ovarian tumours

Mucinous ovarian tumours are sometimes associated with mature teratomas. It is suggested that the mucinous tumours in this setting are derived from teratomas, but there remains the possibility of collision or metastasis from extra-ovarian sites. Because mature ovarian teratomas are considered to be parthenogenetic tumours that arise from a single oocyte/ovum, they have only a maternal genome and therefore show maternal genome imprinting. If mucinous ovarian tumours originate from teratomas, their genome imprinting is theoretically maternal. One of the most important mechanisms of genome imprinting is DNA methylation. In the present study, we analysed a total of 28 mucinous ovarian tumours (7 with teratomas, 21 without teratomas; 14 malignant, 14 borderline) to clarify the methylation profiles of their imprinted genes using methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA) of 21 imprinting control regions (ICRs) of nine imprinted genes/gene clusters using formalin-fixed, paraffin-embedded samples. All cases lacked evidence of an extra-ovarian primary mucinous tumour. In all seven mucinous tumours with teratomas, the overall methylation profile of mucinous tumours was comparable to that of teratomas, although some ICRs showed aberrant methylation. In contrast, all but one of the mucinous tumours without teratomas showed somatic or irregular methylation patterns. Morphologically, there was little teratomatous tissue in some mucinous tumours carrying teratoma-type methylation profiles, suggesting that mucinous tumours overwhelmed ancestral teratomas. In conclusion, the methylation profile of imprinted genes provides evidence that a subset of mucinous ovarian tumours originated from mature teratomas. Genome imprinting-based analysis is a promising strategy to verify the teratomatous origin of human tumours. © 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

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.

What recent primary studies tell us about ovarian teratomas in children: a scoping review

Our knowledge of ovarian teratomas in children is still far from complete, and much remains to be discovered. Here, we conduct a scoping review of the primary research related to ovarian teratomas in pediatric age. To our knowledge, there is no published synthesis of the literature surrounding ovarian teratomas in children using scoping review methodology. We identified 24 studies from 11 countries; 18 studies were retrospective, 3 were prospective, and 3 were experimental. There were 6 studies concerning mature teratomas, 5 concerning immature teratomas, and 13 that included both tumor types. Overall, 9 out of all the studies concerned more than 50 patients. We revealed 7 major branches of research within the topic of ovarian teratoma in pediatric population: recurrence rate/relapse and follow-up strategy, malignant potential, prognostic factors, use of sparing surgery, differences between the use of laparoscopy and laparotomy, use of chemotherapy, and additional examinations to test the character of the lesion (immature vs. mature). This scoping review has revealed a number of knowledge gaps in the evidence base for pediatric ovarian teratomas. Overall, this topic has not been extensively explored, and more research dedicated exclusively to this tumor and patient population is required.

Lack of genetic homozygosity in prepubertal teratomas: divergent pathogenesis distinct from that of teratomas in adolescents

In adults, both immature and mature ovarian teratomas show frequent genetic homozygosity consistent with tumorigenesis involving germ cells after meiosis I. Investigation into genetic zygosity of various teratomas in children has been limited. Thirteen sacrococcygeal, 12 ovarian, and 3 testicular teratomas in children 18 years or younger were retrieved from our departmental archives and histologically reviewed. Tumor and paired normal tissues were microdissected and subjected to short tandem repeat (STR) genotyping. DNA genotyping was informative in 12 sacrococcygeal teratomas, 8 ovarian teratomas, and 3 testicular teratomas. Sacrococcygeal teratomas included seven mature teratomas, four immature teratomas, and one mixed germ cell tumor with patient age ranging from 0 days to 3 years. All but two patients were female. Ovarian teratomas included five mature and three immature teratomas with patient age ranging from 2 to 18 years. Testicular teratomas included two mature teratomas and one immature teratoma with patient age ranging from 3 months to 3 years. All sacrococcygeal, testicular, and ovarian teratomas in patients younger than 4 years showed no evidence of genetic homozygosity by STR genotyping. In contrast, all four ovarian teratomas in patients older than 9 years showed either partial or complete homozygosity. In conclusion, unlike adolescent and adult ovarian teratomas, prepubertal sacrococcygeal and gonadal teratomas lack genetic homozygosity, supporting the hypothesis that teratomas before puberty develop at an early stage of germ cell development different from that of teratomas in adolescents and adults.

Multiregion exome sequencing of ovarian immature teratomas reveals 2N near-diploid genomes, paucity of somatic mutations, and extensive allelic imbalances shared across mature, immature, and disseminated components

Immature teratoma is a subtype of malignant germ cell tumor of the ovary that occurs most commonly in the first three decades of life, frequently with bilateral ovarian disease. Despite being the second most common malignant germ cell tumor of the ovary, little is known about its genetic underpinnings. Here we performed multiregion whole-exome sequencing to interrogate the genetic zygosity, clonal relationship, DNA copy number, and mutational status of 52 pathologically distinct tumor components from ten females with ovarian immature teratomas, with bilateral tumors present in five cases and peritoneal dissemination in seven cases. We found that ovarian immature teratomas are genetically characterized by 2N near-diploid genomes with extensive loss of heterozygosity and an absence of genes harboring recurrent somatic mutations or known oncogenic variants. All components within a single ovarian tumor (immature teratoma, mature teratoma with different histologic patterns of differentiation, and yolk sac tumor) were found to harbor an identical pattern of loss of heterozygosity across the genome, indicating a shared clonal origin. In contrast, the four analyzed bilateral teratomas showed distinct patterns of zygosity changes in the right versus left sided tumors, indicating independent clonal origins. All disseminated teratoma components within the peritoneum (including gliomatosis peritonei) shared a clonal pattern of loss of heterozygosity with either the right or left primary ovarian tumor. The observed genomic loss of heterozygosity patterns indicate that diverse meiotic errors contribute to the formation of ovarian immature teratomas, with 11 out of the 15 genetically distinct clones determined to result from nondisjunction errors during meiosis I or II. Overall, these findings suggest that copy-neutral loss of heterozygosity resulting from meiotic abnormalities may be sufficient to generate ovarian immature teratomas from germ cells.

Multiple Bilateral Ovarian Mature Cystic Teratomas with Ovarian Torsion: A Case Report

Ovarian tumors are a common form of neoplasm in women. Mature cystic teratoma is the most common type, with a bilateral incidence of 8-15%. However, few cases are reported as bilateral and multiple. A rare case of bilateral multiple dermoid cysts in a 19-year-old female patient presented with abdominal pain of one-day duration. Her medical history was unremarkable. Ultrasonography showed multiple bilateral ovarian cystic masses. The patient underwent laparotomy. The masses were excised while preserving the remaining ovarian tissue. Histopathology confirmed the diagnosis of multiple mature cystic teratomas with no presence of malignant tissue.

Chondroid nodule in the female peritoneum arises from normal tissue and not from teratoma or conception product

The pathogenesis of benign-looking cartilaginous tissue within the peritoneum is unknown. Chondroid metaplasia of subcoelomic mesenchyme has been suggested, as has been the case for other gynecological diseases such as endometriosis, peritoneal leiomyomatosis, or gliomatosis peritonei, but has never been proven. Chondroid nodules in the peritoneum may represent either teratomatous tissue, fetal rests from a conception product, or metaplasia of pluripotent mesenchymal cells. Herein, the unique genetic characteristics of ovarian teratomas (homozygous at many polymorphic microsatellite loci) versus normal tissues (heterozygous at the same loci) were used to investigate the origin of chondroid nodules in the peritoneum. DNA samples extracted from paraffin-embedded normal peritoneal tissue and chondroid peritoneal nodules from two patients were studied. In both cases, chondroid and normal tissue showed heterozygosity at each informative microsatellite locus on different chromosomes, with a profile similar to the mother. These results indicate that peritoneal chondroid nodules arise within the peritoneum, presumably from pluripotent mesodermal stem cells, and are not related to teratomatous proliferation, or previous pregnancy. This finding shows once again the plasticity and metaplastic potential of stem cells within the peritoneal cavity.

Unusual presentation of plasmablastic lymphoma involving ovarian mature cystic teratoma: a case report

BACKGROUND

Plasmablastic lymphoma (PBL) is relatively new clinical entity described as a distinct subtype of diffuse large B-cell lymphoma (DLBCL). It is characterized by its aggressive nature and proliferation of large neoplastic cells resembling immunoblasts including cells with more obvious plasmacytic differentiation. In this case report, we describe an unexpected finding of PBL associated with a mature cystic teratoma of the ovary in a young immune competent woman.

CASE PRESENTATION

A 19-year old woman was admitted to the hospital with generalized lymphadenopathy, a pelvic tumor mass measuring 35 × 30 cm and a 4 cm lump in her right breast. She underwent a right salpingo-oophorectomy, lymphadenectomy, splenectomy, omentectomy, and a right breast lumpectomy. On macroscopic examination the right ovary was replaced by a thick-walled multilocular cystic tumor. Upon incision, the cysts were filled with thick, greasy sebaceous material and hair and there were several solid nodules within the cyst walls. Histological examination revealed a mature cystic teratoma and malignant non-Hodgkin lymphoma (NHL) within the solid nodules. Tumor tissue from the right breast, spleen and lymph nodes, all had the same histological, NHL morphology. After extensive immunostaining, a diagnosis of PBL was made. Following surgery, the patient was treated with different chemotherapy regimens, without any significant regression of the disease, and died of multiple organ failure.

CONCLUSIONS

Primary NHL of the ovary is relatively rare occurrence while secondary involvement by lymphoma is much more common. PBL is a rare lymphoma, primarily reported in the jaw and oral mucosa, but also documented in extra-oral sites. To the best of our knowledge, this is the first case described in a mature ovarian cystic teratoma. Although the patient was HIV-negative and immune competent, she had progressive disease and died despite aggressive chemotherapy 11 months after the initial diagnosis.

Frequent homozygosity in both mature and immature ovarian teratomas: a shared genetic basis of tumorigenesis

Although homozygosity is well documented in mature teratomas, the genetic zygosity of ovarian immature teratomas and mixed germ cell tumors is less well studied. Ten cases of mature cystic teratomas, eleven cases of grade 2 or 3 immature teratomas, and seven cases of mixed germ cell tumors with an immature teratoma component were investigated by short tandem repeat genotyping to interrogate their genetic zygosity. DNA genotyping was informative in eight mature teratomas, seven immature teratomas and six cases of mixed germ cell tumors. Out of the eight mature teratomas, five cases showed partial or complete homozygosity (63%) with two cases demonstrating complete homozygosity (25%). Of the immature teratomas, six cases showed partial or complete homozygosity (86%) with two cases demonstrating complete homozygosity (29%). For the mixed germ cell tumors, two cases showed partial homozygosity (33%) and none displayed complete homozygosity. Long-term clinical follow-up was available for five immature teratomas (mean follow-up 110 months) and five mixed germ cell tumors (mean follow-up 66 months). None of the five patients with pure immature teratoma had a recurrence; in contrast, four out of five mixed ovarian germ cell tumors recurred between 4 months to 8 years (P=0.048). In conclusion, both immature and mature teratomas harbor frequent genetic homozygosity suggesting a common cellular origin involving germ cells at the same developmental stage. The difference in the rate of homozygosity and tumor recurrence between pure immature teratomas and mixed germ cell tumors suggests that the two entities may involve different pathogenetic pathways and likely pursue different biological behaviors.

Vedolizumab as a Potential Culprit in the Development of Ovarian Teratoma?

Vedolizumab is a new humanized monoclonal antibody that has been reserved for those with moderate-to-severe Crohn's disease and ulcerative colitis who have failed immunomodulator and TNF-α antagonist therapy, and for those who have an increased risk for developing progressive multifocal leukoencephalopathy. Because it targets gastrointestinal tract-specific lymphocytes, meta-analyses and integrated studies have shown that vedolizumab causes fewer extraintestinal adverse effects, such as opportunistic infections and malignancies, compared with anti-TNF therapies. We present the case of a patient who developed an ovarian teratoma after initiation of vedolizumab therapy.

Ovarian Mature and Immature Teratomas in Monozygotic Twins: A Case Report of Simultaneous Presentation

Mature cystic teratoma is one of the most common kinds of ovarian tumor, and immature teratoma is a rare tumor, representing less than 1% of all ovarian teratomas. Although there are some reports about familial occurrences of ovarian tumors, literature concerning the clinical cases of monozygotic twins is rare. We report the 5-year clinical courses of a 12-year-old Japanese girl with a recurrent bilateral ovarian mature teratoma and her monozygotic twin with a unilateral ovarian mature teratoma and contralateral ovarian immature teratoma. This is the first clinical report on mature and immature teratomas of the ovary in monozygotic twins. Our cases support future clarification of the molecular mechanism and pathogenesis of teratoma.

Genetic analysis results of mature cystic teratomas of the ovary in Taiwan disagree with the previous origin theory of this tumor

The most accepted theory regarding mature cystic teratomas of the ovary is that they are of parthenogenetic origin from oocyte after the completion of first division. Our previous study demonstrated that the origin of mature cystic teratoma of the uterus is not related to the parthenogenetic process, but is most likely pluripotential stem cell or primordial germ cell before meiosis I. Further studies are needed to clarify the origin of benign mature cystic teratomas of the ovary in Taiwan. In the present study, we investigated the DNA profiles of 9 mature cystic teratomas of the ovary using short tandem repeat analysis with AmpFLSTR SGM Plus, Profiler PCR amplification kits. The methylation statuses of the HhaI sites in the SNRPN, H19DMR, and KvDMR regions were determined on methylation-sensitive multiplex ligation-dependent probe amplification analysis. DNA profiling data from the 9 mature cystic teratomas of the ovary excluded parthenogenetic origin, as most of the 15 short tandem repeat loci were heterozygous on genotyping. There were varying degrees of hypermethylation of SNRPN gene and KvDMR locus in the presence of maternal uniparental disomy in all 9 mature cystic teratomas of the ovary. In light of these results, we further postulated that the origin of these mature cystic teratomas of the ovary is oogonia or primary oocyte before germinal vesicle stage failure of meiosis I.

Case Study: Diffuse Large B-Cell Lymphoma Arising in Ovarian Mature Cystic Teratoma

We describe an unexpected finding of diffuse large B-cell lymphoma associated with mature cystic teratoma of the ovary. A 68-yr-old woman with a complex left ovarian cystic mass on imaging underwent bilateral salpingo-oophorectomy, lymphadenectomy, appendicectomy, and omentectomy. Histopathologic examination revealed nodules of malignant non-Hodgkin lymphoma within the teratoma. A diagnosis of diffuse large B-cell lymphoma, germinal center cell subtype by Hans criteria was made after immunostaining and molecular studies. The patient was treated with R-CHOP chemotherapy and remains disease-free at 14-mo follow-up.

Peritoneal and nodal gliomatosis with endometriosis, accompanied with ovarian immature teratoma: a case study and literature review

Gliomatosis peritonei (GP) indicates the peritoneal implantation of mature neuroglial tissue and is usually accompanied by ovarian mature or immature teratoma. Here, we report a case of ovarian immature teratoma associated with gliomatosis involving the peritoneum, lymph nodes and Douglas' pouch, where gliomatosis coexisted with endometriosis. As far as we know, only seven cases of GP have been reported as coexisting with endometriosis. Eight cases with mature glial tissue in the lymph nodes, i.e., nodal gliomatosis, have been published either in association with GP or in its absence. Metaplasia of pluripotent coelomic stem cells has been suggested to be responsible for the pathogenesis of endometriosis and GP rather than implantation metastases of ovarian teratomatous tumor with varying maturation. This theory is also applied to GP independently of ovarian teratomatous tumors. To the best of our knowledge, nodal gliomatosis coexisting with GP and also involving endometriosis has not yet been reported.

Renal medullary carcinoma: molecular, immunohistochemistry, and morphologic correlation

Renal medullary carcinoma, a highly aggressive tumor mainly occurring in patients with sickle cell hemoglobinopathy, is characterized by advanced stage at the time of presentation and poor response to treatment. Currently, the pathogenesis of this tumor is not well understood. In this study, the clinicopathologic features and molecular changes of 15 renal medullary carcinoma cases were evaluated. These cases demonstrated male predominance (M:F=2:1) with a median age of 26 years. The tumors occurred predominantly in the right kidney with an average size of 5.9 cm. Immunohistochemistry analysis showed that the neoplastic cells were positive for CEA (7/8), AE1/3 (8/8), CAM5.2 (7/7), CK7 (5/5), CK20 (4/6), and vimentin (6/6). Absence of SMARCB1 protein expression in tumor cells was demonstrated in all of the 7 cases analyzed. By polymerase chain reaction-based microsatellite analysis, loss of heterozygosity of SMARCB1 was identified in 9 of 10 cases. These data suggest that inactivation of SMARCB1 may play a role in the pathogenesis of renal medullary carcinoma.

Lessons from human teratomas to guide development of safe stem cell therapies

The potential for the formation of teratomas or other neoplasms is a major safety roadblock to clinical application of pluripotent stem cell therapies. Preclinical assessment of the risk of tumor formation in this context poses considerable scientific and regulatory challenges, especially because animal xenograft models may not properly reflect the long-term tumorigenic potential of human cells. A better understanding of the biology of spontaneously occurring teratomas and related tumors in humans can help to guide efforts to assess and minimize the potential hazards of embryonic stem cell or induced pluripotent stem cell therapeutics. Here we review the features of teratomas derived experimentally from human pluripotent stem cells and argue that they most closely resemble spontaneous benign teratomas that occur early in both mouse and human life. The natural history and pathology of these spontaneously occurring teratomas provide important clues for preclinical safety assessment and patient monitoring in trials of stem cell therapies.

Molecular genetic evidence supporting the neoplastic nature of fibrous stroma in testicular teratoma

Testicular teratoma typically consists of heterogeneous mixtures of diverse epithelial and stromal components. The biological nature and genetic characteristics of the fibrous stroma of testicular teratomas have not been thoroughly investigated. Chromosome 12p abnormalities are the hallmark genetic alterations of germ cell tumors. We studied chromosome 12p abnormalities in the fibrous stroma and other components of pure testicular teratomas from 32 patients using interphase fluorescence in situ hybridization. Overall, 72% (23/32) of pure testicular teratomas had chromosome 12p abnormalities. Isochromosome 12p or 12p overrepresentation independent of isochromosome 12p was detected in the fibrous stroma in 53% (17/32) and 41% (13/32) of cases, respectively. Among the 17 cases positive for isochromosome 12p, 8 (47%) also had 12p overrepresentation. In 31% (10/32) cases, the fibrous stroma showed neither 12p overrepresentation nor isochromosome 12p. Isochromosome 12p and 12p overrepresentation were identified, respectively, in the gastrointestinal-type epithelium of 14/23 (61%) and 15/23 (65%) cases; in the respiratory-type epithelium of 41% (7/17) and 41% (7/17) cases; in the squamous epithelium of 62% (8/13) and 54% (7/13) cases; and in the cartilage of 63% (5/8) and 38% (3/8) cases. Concordant chromosomal 12p abnormalities were observed between the fibrous stroma and epithelial elements of testicular teratomas. Our results indicate that the fibrous stroma of testicular teratomas frequently has genetic abnormalities similar to those of the epithelial components. Concordant chromosome 12p alterations between the fibrous stroma and epithelial elements provide further evidence that both epithelial and fibrous components of teratoma are derived from a common progenitor.

Intrathoracic glial implants in a child with gliomatosis peritonei

Glial peritoneal implants, commonly referred to as gliomatosis peritonei, are an occasional feature of ovarian teratomas. They are benign nodules of mature glial tissue and usually do not adversely affect outcome. We present the case of a 12-year-old girl who underwent excision of an immature ovarian teratoma, along with biopsies of multiple glial peritoneal implants. She also had a 2-cm right-sided pleural mass, which turned out to be normal glial tissue that was histologically indistinguishable from the peritoneal glial tissue. Pleural gliomatosis has not been described in the literature. The pathophysiology of gliomatosis peritonei was originally thought to be the direct extrusion or lymphatic spread of glial cells from the associated teratoma, although it has been postulated that the glial implants may instead be the result of pluripotent Mullerian stem cells that undergo metaplasia. This report provides evidence to bolster the metaplastic theory.

Recent Advances in the Pathology and Classification of Ovarian Germ Cell Tumors

In recent years, our knowledge of ovarian germ cell tumors has increased, and their classification has evolved. The introduction of cisplatin-based chemotherapy and the discovery of tumor markers, including alpha-fetoprotein and human chorionic gonadotropin, have dramatically changed the clinical outlook for most of these patients. In this review, recent advances in the classification and pathology of ovarian germ cell tumors are discussed. Where appropriate, comparisons are made with testicular germ cell tumors. The last section of the article discusses the pathogenesis of germ cell tumors. This review will emphasize the articles written in the last 10 years and those that have significantly advanced our knowledge of germ cell tumors in past decades.

Analysis of ovarian teratomas for isochromosome 12p: evidence supporting a dual histogenetic pathway for teratomatous elements

Teratomas are the most common germ cell tumor (GCT) of the ovary and include several types with a range of clinical behavior. As in testicular teratomas, they may be benign, malignant or a component of a mixed GCT. In the testis, data support separate pathogeneses for prepubertal and postpubertal teratomas, with derivation of the former from a nontransformed germ cell and the latter from differentiation of a nonteratomatous, malignant GCT. The absence of cytogenetic abnormalities (including isochromosome 12p (i(12p)) in mature ovarian teratomas suggests that they may be analogous to prepubertal testicular teratomas, but there are no data regarding genetic changes in the teratomatous components of ovarian mixed GCTs. We therefore studied the teratomatous components of six mixed GCTs of the ovary using fluorescence in situ hybridization (FISH) for i(12p). Six mixed GCTs of the ovary occurred in patients 4-33 years of age; all had teratomatous and yolk sac tumor components and three also contained foci of embryonal carcinoma. Using FISH with 12p telomeric and 12 centromeric probes, five of six (83%) cases had detectable i(12p) in their nonteratomatous components, and four of six (66%) in the teratomatous component. One of the two cases without demonstrable i(12p) in the teratomatous portion of the mixed GCT also did not have identifiable 12p abnormalities in other elements of the mixed GCT. By comparison, five pure, mature ovarian teratomas and three pure, immature ovarian teratomas showed no evidence of either i(12p) or other forms of 12p amplification. These findings support that teratoma in mixed ovarian GCTs has a different pathogenesis compared to pure teratoma of the ovary. Furthermore, the findings of i(12p) in both the teratomatous and nonteratomatous components of ovarian mixed GCTs supports that the teratoma derives from other components, similar to the situation in the testis.

Germ cell tumors of the gonads: a selective review emphasizing problems in differential diagnosis, newly appreciated, and controversial issues

Gonadal germ cell tumors continue to be the cause of diverse, diagnostically challenging issues for the pathologist, and their correct resolution often has major important therapeutic and prognostic implications. They are academically interesting because of the biological diversity exhibited in the two gonads and variation in frequency of certain neoplasms. The most dramatic examples of the latter are the frequency of dermoid cyst in the ovary compared to the testis and the reverse pertaining to embryonal carcinoma. Within the teratoma group, there is strong evidence that ovarian and prepubertal testicular teratomas are derived from benign germ cells, a pathogenesis that likely applies also to the rare dermoid cysts and uncommon epidermoid cysts of the testis. In contrast, postpubertal testicular teratomas derive from malignant germ cells, specifically representing differentiation within a preexistent nonteratomatous cancer. As expected, given the foregoing, teratomas in boys are clinically benign, whereas in postpubertal males they are malignant, independent of their degree of immaturity. On the other hand, immaturity is an important finding in ovarian teratomas, irrespective of age, although its significance in children has recently been challenged. It is usually recognized on the basis of embryonic-appearing neuroepithelium, which shows mitotic activity and apoptosis in contrast to differentiated neuroepithelial tissues, which may occur in mature ovarian teratomas. Rarely it is based on the presence of cellular, mitotically active glial tissue. Fetal-type tissues alone are not sufficient for a diagnosis of immature teratoma. Further differences between the teratomatous tumors in the two gonads are the relative frequency of monodermal teratomas in the ovary in contrast to the testis, where only one subset, carcinoids, is seen with any frequency. When uncommon somatic-type malignancies (usually squamous cell carcinoma) occur in mature cystic teratomas of the ovary, this is a de novo form of malignant transformation; similar tumors in the testis, a very rare event, represent overgrowth of teratomatous elements that originated from malignant, nonteratomatous germ cell tumors and, therefore, had previously undergone malignant transformation. Germinomas may have several unusual features in each gonad; these include microcystic arrangements that suggest yolk sac tumor, tubular patterns that mimic Sertoli cell tumor, apparent increased cytological atypia that causes concern for embryonal carcinoma, and prominent syncytiotrophoblast giant cells that suggest choriocarcinoma. Awareness of these variants, good technical preparations, the retained typical cytological features of germinoma cells, and the judicious use of tailored panels of immunohistochemical stains resolve these dilemmas in virtually all instances. Two aspects of germinomas are unique to the testis. Firstly, intertubular growth of small seminomas may cause them to be overlooked. Secondly, the distinctive spermatocytic seminoma occurs only in the testis. A newly recognized aspect of this tumor is the propensity for some to be relatively monomorphic, making them apt to be mistaken for usual seminoma or embryonal carcinoma, although the characteristic polymorphic appearance in some foci, absence of intratubular germ cell neoplasia, unclassified type, and immunohistochemical stains should prevent this error. Cytoplasmic membrane immunoreactivity for placental alkaline phosphatase and CD117, with usual negativity for AE1/AE3 cytokeratins, is helpful in the diagnosis of germinoma. The recently described marker, OCT3/4, a nuclear transcription factor, is especially helpful in the differential of germinoma and embryonal carcinoma with other neoplasms. Yolk sac tumor continues to be confused occasionally with clear cell carcinoma of the ovary. Glandular ('endometrioid-like') yolk sac tumors mimic endometrioid carcinomas; predominant or pure hepatoid yolk sac tumors cause concern for metastatic hepatocellular carcinoma or, in the ovary, primary hepatoid carcinoma, and solid patterns, especially in limited samplings, may be misinterpreted as germinoma. The usually younger age of patients with yolk sac tumors helps with the differential considerations with the nongerm cell tumors, as do other clinical and microscopic features and selected immunohistochemical stains. Choriocarcinoma is rare in both gonads, and those in the ovary must be distinguished from metastatic tumors of placental origin. Syncytiotrophoblast cells alone, admixed with other forms of germ cell tumor, still are confused with choriocarcinoma, but this phenomenon, which is much more frequent than choriocarcinoma, lacks the plexiform arrangement of different trophoblast cell types that typifies the latter. Mixed germ cell tumors (which may show almost any combination of components) are common in the testis but rare in the ovary. A separately categorized, rare form of mixed germ cell tumor seen in both gonads is the polyembryoma. It is perhaps the most photogenic of all gonadal germ cell tumors and is also intriguing because of its distinctive, organized arrangement of yolk sac tumor and embryonal carcinoma elements and recapitulation of very early embryonic development, even to the extent of having in its fundamental unit, the embryoid body, a miniature yolk sac, and amniotic cavity. These tumors, which are constituted by innumerable embryoid bodies, almost always contain teratomatous glands in minor amounts, and one way of viewing the polyembryoma is to consider it the most immature form of teratoma. Embryoid bodies are also common as a minor component of many mixed germ cell tumors, particularly in the testis, and the diffuse embryoma is another variant that has a particular arrangement of yolk sac tumor and embryonal carcinoma elements. Regression of gonadal germ cell tumors is a phenomenon restricted to the testis, for unknown reasons. These so-called 'burnt-out' germ cell tumors can be recognized by a distinctive constellation of findings, including sometimes minor foci of residual recognizable germ cell neoplasia, a well-defined zone of scarring (often having residual ghost tubules), associated lymphoplasmacytic infiltrate, intratubular calcification and, in about 50%, of in situ germ cell neoplasia.

Nephroblastoma Arising in a Germ Cell Tumor of Testicular Origin

We report a nephroblastoma arising in a germ cell tumor of testicular origin occurring in a 22-year-old man. Orchiectomy demonstrated a malignant mixed germ cell tumor composed of mature and immature teratoma with nephroblastoma and rhabdomyosarcoma. Following chemotherapy, the patient developed supraclavicular and retroperitoneal lymphadenopathy. Excision demonstrated metastatic teratoma at both sites. No recurrence was noted with 21 months of additional follow-up. Using tissue microdissection and loss of heterozygosity analysis, we investigated the clonality of the mature teratoma, immature teratoma, nephroblastoma, and rhabdomyosarcoma components of the primary tumor and of the metastatic mature teratoma at the two separate distant sites. Nine microsatellite polymorphic makers were used to examine the pattern of allelic loss in both primary and metastatic tumors. Loss of heterozygosity was found in 4 DNA loci, and the same pattern of allelic loss was demonstrated at all 4 loci in all of the different components of the primary tumor and the metastatic mature teratomas, supporting the germ cell tumor origin of the nephroblastoma component. Loss of heterozygosity on chromosome 17p13 (TP53) was detected in metastatic mature teratoma, but not in the primary tumor. Loss of heterozygosity was observed at 11p13, the locus of WT1 inactivation in patients genetically predisposed to nephroblastoma, and this loss may be an important genetic mechanism in nephroblastomatous differentiation of germ cell tumors. These data support a common clonal origin for nephroblastoma and the other germ cell tumor components.

Gonadal teratomas: a review and speculation

Teratomas of the ovary and testis are confusing because, despite histologic similarities, they exhibit different biologic behaviors, depending mostly on the site of occurrence and the age of the patient. Thus, most ovarian teratomas are benign, and most testicular teratomas are malignant, with the exception of those occurring in children. These general statements, however, do not hold true for ovarian teratomas that are "immature" or exhibit "malignant transformation" and for dermoid and epidermoid cysts of the testis, categories of ovarian and testicular teratomas that are malignant and benign, respectively. This review concentrates on some of the "newer" observations concerning these interesting and confusing neoplasms, including diagnostically deceptive patterns. It is the author's opinion that much of the confusion regarding gonadal teratomas can be clarified by the concept that the usual ovarian teratoma derives from a benign germ cell in a parthenogenetic-like fashion, whereas the typical postpubertal testicular example derives from a malignant germ cell, mostly after evolution of that originally malignant cell to an invasive germ cell tumor (ie, embryonal carcinoma, yolk sac tumor, etc). The postpubertal testicular teratomas can therefore be thought of as an end-stage pattern of differentiation of a malignant germ cell tumor. The pediatric testicular teratomas, as well as dermoid and epidermoid cysts of the testis, however, must derive from benign germ cells, in a fashion similar to most ovarian teratomas. The teratomatous components of mixed germ cell tumors of the ovary, on the other hand, likely have a pathogenesis similar to that of postpubertal testicular teratomas.

Multilineage potential of homozygous stem cells derived from metaphase II oocytes

Human stem cells derived from human fertilized oocytes, fetal primordial germ cells, umbilical cord blood, and adult tissues provide potential cell-based therapies for repair of degenerating or damaged tissues. However, the diversity of major histocompatibility complex (MHC) antigens in the general population and the resultant risk of immune-mediated rejection complicates the allogenic use of established stem cells. We assessed an alternative approach, employing chemical activation of nonfertilized metaphase II oocytes for producing stem cells homozygous for MHC. By using F1 hybrid mice (H-2-B/D), we established stem cell lines homozygous for H-2-B and H-2-D, respectively. The undifferentiated cells retained a normal karyotype, expressed stage-specific embryonic antigen-1 and Oct4, and were positive for alkaline phosphatase and telomerase. Teratomatous growth of these cells displayed the development of a variety of tissue types encompassing all three germ layers. In addition, these cells demonstrated the potential for in vitro differentiation into endoderm, neuronal, and hematopoietic lineages. We also evaluated this homozygous stem cell approach in human tissue. Five unfertilized blastocysts were derived from a total of 25 human oocytes, and cells from one of the five hatched blastocysts proliferated and survived beyond two passages. Our studies demonstrate a plausible "homozygous stem cell" approach for deriving pluripotent stem cells that can overcome the immune-mediated rejection response common in allotransplantation, while decreasing the ethical concerns surrounding human embryonic stem cell research.

Glial implants in gliomatosis peritonei arise from normal tissue, not from the associated teratoma

Metaplasia of subcoelomic mesenchyme has been implicated, but not proven, in the pathogenesis of common gynecological diseases such as endometriosis and rarer entities such as leiomyomatosis peritonealis disseminata and gliomatosis peritonei (GP). GP is associated with ovarian teratomas and is characterized by numerous peritoneal and omental implants composed of glial tissue. Two theories to explain the origin of GP have been proposed. In one, glial implants arise from the teratoma, whereas in the other, pluripotent Müllerian stem cells in the peritoneum or subjacent mesenchyme undergo glial metaplasia. To address the origin of GP, we exploited a unique characteristic of many ovarian teratomas: they often contain a duplicated set of maternal chromosomes and are thus homozygous at polymorphic microsatellite (MS) loci. In contrast, DNA from matched normal or metaplastic tissue (containing genetic material of both maternal and paternal origin) is expected to show heterozygosity at many of these same MS loci. DNA samples extracted from paraffin-embedded normal tissue, ovarian teratoma and three individual laser-dissected glial implants were studied in two cases of GP. In one case, all three implants and normal tissue showed heterozygosity at each of three MS loci on different chromosomes, whereas the teratoma showed homozygosity at the same MS loci. Similar results were observed in the second case. Our findings indicate that glial implants in GP often arise from cells within the peritoneum, presumably pluripotent Müllerian stem cells, and not from the associated ovarian teratoma. This finding has important implications for more common gynecological entities with debatable pathogenesis, such as endometriosis, by definitively demonstrating the metaplastic potential of stem cells within the peritoneal cavity.

Biovularity and "coalescence of primary follicles" in ovaries with mature teratomas

Several theories have been postulated regarding the origin of ovarian teratomas, including incomplete twinning, neoplastic proliferation of sequestered totipotent blastomeres or primordial cells, derepression of totipotent genetic information in the nuclei of somatic cells, and parthenogenetic development of germ cells. At present parthenogenetic development of ova is the most widely accepted theory, primarily because of the presence of a 46 XX karyotype in almost all mature teratomas. However, some authors have raised the possibility of fusion of ova in the mechanism of formation of ovarian teratomas. We report the results of a study on ovarian tissue adjacent to 31 teratomas to assess the frequency of biovularity, which could provide evidence favoring the last theory. On the whole we found biovularity in 26 ovaries of young patients (mean age, 27 years) with variable numbers of biovular follicles ranging from 1 in 4 cases to more than 10 in 2 cases; the number of biovular follicles depended on the quantity of ovarian tissue examined as well as on the total number of ova in the tissue. In multiple occasions 2 ova were included within a single follicle; in 24 ovaries the biovularity was correlated with coalescence of primary follicles characterized morphologically by an ovoid or hourglass-like shape that resulted from cohesion of 2 follicles. As control cases, 30 ovaries of patients with an average age of 28 years were examined (12 removed for endometriosis, 8 for serous cystadenoma, 7 for tubal pregnancy, and 3 for acute salpingo-oophoritis). Only 1 ovary with endometriosis contained a single biovular follicle. The results suggest that ovarian teratoma development may result from fusion of ova in ovaries containing biovularity and phenomena of coalescence of primary follicles.

Teratomatous genotype detected in malignancies of a non-germ cell phenotype

Originating from post-meiotic germ cells, mature ovarian teratomas (MOT) are genetically homozygous tumors within heterozygous hosts. MOT may be associated with malignant tumors of a non-germ cell phenotype (so-called malignant transformation). Based on the presence of in situ changes, some cases have been hypothesized to arise from teratomatous tissue. However, other malignancies associated with mature teratomas, such as sarcomas, may originate from either teratomatous elements or preexisting somatic ovarian tissue. Eight cases of MOT containing various histologic types of malignancy, including four squamous cell carcinomas, two sarcomas, one thyroid carcinoma, and one carcinoid tumor, were selected for study. Using selective tissue microdissection and PCR-based analysis of the extracted DNA, we compared the genotypic pattern of the mature teratomatous components to the associated malignant neoplasm with a random panel of highly informative genetic markers for different chromosomes. In all eight cases, genetic analysis of the malignant component revealed a homozygous genotype. In seven cases, the genetic profiles of mature teratomas and the associated malignant tumors were identical, suggesting a direct pathogenetic relationship between these lesions. In one case, the malignant component revealed homozygosity of different alleles compared with mature teratoma, suggesting independent teratomatous growth processes. This finding indicates that some ovarian malignancies of the non-germ cell phenotype arise in teratoma and fall into the spectrum of germ cell tumors.