"Embryonic-type Neuroectodermal Tumor" Should Replace "Primitive Neuroectodermal Tumor" of the Testis and Gynecologic Tract: A Rationale for New Nomenclature

Ewing Sarcoma of the Female Genital Tract: Clinicopathologic Analysis of 21 Cases With an Emphasis on the Differential Diagnosis of Gynecologic Round Cell, Spindle, and Epithelioid Neoplasms

Ewing sarcoma is an uncommon neoplasm considered in the differential diagnosis of tumors with "small round cell" morphology, but its occurrence in the gynecologic tract has only been sporadically documented. Herein, we describe the largest cohort of Ewing sarcoma localized to the female genital tract to date, and emphasize their clinicopathologic resemblance to more common gynecologic neoplasms. Ewing sarcoma (n=21) was retrospectively identified from 5 institutions. The average patient age was 35 (range 6-61) years. Tumor sites included uterus (n=8), cervix (n=4), vulva (n=5), vagina (n=1), broad ligament (n=1), inguinal area (n=1), and pelvis (n=1). Nine of 18 cases in which slides were available for review demonstrated only classic round cell morphology, with the remainder showing a variable combination and prominence of variant ovoid/spindle or epithelioid appearance. Tumors showed diffuse membranous reactivity for CD99 (20/20) and were positive for NKX2.2 (8/8, diffuse) and cyclin D1 (7/7, of which 3/7 were patchy/multifocal and 4/7 were diffuse). They were negative for ER (0/6) and CD10 (0/6). Three cases were initially diagnosed as endometrial stromal sarcomas. EWSR1 rearrangement was confirmed in 20/21 by fluorescence in situ hybridization (n=15) and/or sequencing (n=8). Of the eight tumors that underwent sequencing, 6 harbored FLI1 , 1 ERG, and 1 FEV as the fusion partner. Of 11 patients with available follow-up, 5 died of disease, 1 developed lung metastases and 5 are alive with no evidence of disease. Ewing sarcoma of the gynecologic tract is a rare, aggressive entity that shares some morphologic and immunohistochemical features with other more common gynecologic neoplasms. In addition to the typical round cell appearance, variant spindled/ovoid to epithelioid morphology may also be observed and should prompt consideration of this entity with appropriate immunohistochemical and/or molecular studies.

Primitive Embryonic-Type Neuroectodermal/Glandular Complexes in Testicular Germ Cell Tumors: A Mimic of Embryonic-Type Neuroectodermal Tumor

Embryonic-type neuroectodermal elements are often intimately mixed with primitive endodermal-type glands, like those of yolk sac tumors, in germ cell neoplasia in situ (GCNIS)-derived germ cell tumors of the testis. Because the primitive glands mimic tubules or rosettes of embryonic-type neuroectodermal elements, these embryonic-type neuroectodermal/glandular complexes may be misinterpreted as pure lesions of embryonic-type neuroectodermal elements, which, if of sufficient size, may lead to a diagnosis of embryonic-type neuroectodermal tumor, despite that the criteria of the World Health Organization for a "somatic-type malignancy" are not met. A diagnosis of embryonic-type neuroectodermal tumor in the testis may lead to retroperitoneal lymphadenectomy even in clinical stage I patients, and in postchemotherapy resections indicates a poor prognosis. The distinction of the neuroectodermal and glandular elements is not always straightforward based on morphology alone. We, therefore, studied 34 testis-derived germ cell tumors with embryonic-type neuroectodermal/glandular complexes and 2 purely glandular yolk sac tumors to characterize the immunophenotypes and determine an efficient immunohistochemical panel to aid in this differential. We found that GFAP, synaptophysin, and paired-like homeobox 2B (PHOX2B) expression was specific to embryonic-type neuroectodermal elements, although PHOX2B had poor sensitivity. In contrast, positive reactions with antibodies directed against AFP, villin, and CDX2 were specific for the glandular elements, although CDX2 had poor sensitivity. Other markers, including AE1/AE3 cytokeratin, SALL4, glypican 3, SOX2, SOX11, CD56, INSM1, and neurofilament, proved less helpful because of their nonspecificity and/or poor sensitivity. We conclude that the optimal immunohistochemical panel for distinguishing the components of embryonic-type neuroectodermal/glandular complexes includes stains for synaptophysin, GFAP, villin, and AFP.

Diffuse Pediatric-type High-grade Glioma Arising in an Ovarian Mature Cystic Teratoma

Immature neuroectodermal tissue can be found in the ovary as part of an immature teratoma or as part of a teratoma with malignant neuroectodermal transformation. Such lesions may closely resemble central nervous system tumors, but their biologic similarity is unclear. We describe an 18-yr-old female who presented with abdominal pain caused by an ovarian mass with widespread metastases. Histology showed a primitive, high-grade tumor arising in the background of a mature teratoma. The tumor was SOX10 positive, with focal expression of GFAP, S100, NSE, and synaptophysin. Molecular analysis demonstrated co-amplification of PDGFRA and KIT , alterations common in high-grade gliomas. By whole-genome methylation profiling, it clustered into the "diffuse pediatric-type high-grade glioma, RTK1 subtype, subclass c" group. Despite progressing through 2 lines of chemotherapy with widespread metastatic disease, she achieved an excellent response to chemotherapy directed toward aggressive germ cell tumors. This case emphasizes the importance of immunohistochemical, genomic, and epigenetic analyses to accurately classify these exceedingly rare tumors and determine the optimal therapy.

Testicular cancer: new developments, molecular pathology, and current research keynote

Germ cell tumors (GCTs) are now considered a curable cancer, with a > 95% cure rate in all patients and about 90% cure rate in patients with metastatic disease. The success of physicians in curing the disease is underpinned by multidisciplinary advances. Of relevance in this regard are the nowadays-applied homogeneous terminology based on pathologically better characterized testicular neoplasms and the development of a widely used risk stratification model for metastatic disease introduced by the International Germ Cell Cancer Collaborative Group in 1997 and updated in 2021. Non-pulmonary visceral metastases, high levels of the serum tumor markers alpha-fetoprotein (AFP) and human chorionic gonadotropin (HCG), and primary mediastinal non-seminoma are currently identified as determinants of poor prognosis. In addition, the presence of distinct microRNA profiles between seminomas and non-seminoma GCTs has opened up important perspectives in terms of noninvasive biomarkers that can be used in diagnosis and treatment monitoring.

Reprint of: somatic-type malignancies in testicular germ cell tumors

The development of somatic-type malignancy (SM) in testicular germ cell tumor represents a major challenge in the diagnosis and treatment of testicular cancer. Most SMs are derived from teratoma, and the remainder is associated with yolk sac tumor. They occur more frequently in metastases than in primary testicular tumors. SMs demonstrate a variety of histologic types, including sarcoma, carcinoma, embryonic-type neuroectodermal tumor, nephroblastoma-like tumor, and hematologic malignancy. Sarcoma, particularly rhabdomyosarcoma, accounts for the majority of SMs in the primary testicular tumors, whereas carcinoma, particularly adenocarcinoma, is the most common SM in metastases. Although SMs derived from testicular germ cell tumors mimic their histologic counterparts in other organs with overlapping immunohistochemical profiles, isochromosome 12p is present in most SMs, which can be useful in the differential diagnosis. The presence of SM in the primary testicular tumor may not worsen the outcome, but the development of SM in metastasis is associated with a poor prognosis. Furthermore, somatic-type carcinoma is likely associated with a worse prognosis than somatic-type sarcoma. Although SMs respond poorly to the cisplatin-based chemotherapy, timely surgical resection is an effective treatment for most patients.

Transformed Testicular Teratoma to Embryonic-Type Neuroectodermal Tumor With Metastasis to Mediastinum

Testicular teratomas may present in both prepubertal and adult men; however, the prognosis differs greatly between these 2 populations. In children, teratomas (prepubertal type) most often occur before the age of 4, are generally seen in their pure form, and behave in a benign fashion. In adults (postpubertal type), teratomas are usually part of a mixed germ cell tumor, and they have the potential to be found at metastatic sites, especially following chemotherapy for non-teratomatous germ cell tumor. Analyses of metastases from germ cell tumors and teratomas from the same patient have demonstrated a high degree of concordance in the observed genetic abnormalities. In rare cases, testicular teratoma can transform into a malignant germ cell tumor. One such type of transformation is into a primitive neuroectodermal tumor. These tumors are malignant and often metastasize to the retroperitoneum but may also metastasize to other sites. A multimodal treatment approach is needed, including surgery and adjuvant chemotherapy. We describe a rare case of malignant transformation of a testicular teratoma into a primitive neuroectodermal tumor with metastasis to the mediastinum. The patient was treated with radical orchiectomy, retroperitoneal lymph node dissection, and adjuvant vincristine, adriamycin, and cyclofosfamide alternating with ifosfamide and etoposide (VAC/IE therapy).

Unresectable Metastatic Testicular Germ Cell Tumor With Low-grade Neuroglial Neoplasm, Stable After Radiation and Chemotherapy

We present an 18-year-old male patient who presented with a 16 cm testicular tumor alongside multiple lesions in the lungs, right pelvis with involvement of the ischio/pubic bone, and enlarged pelvic lymph nodes on imaging, suspicious for metastatic disease. Histologic and immunohistochemical examinations revealed an embryonic type neuroectodermal tumor (somatic-type malignancy, 10%) arising in a malignant mixed germ cell tumor composed of teratoma (50%), embryonal carcinoma (10%) and yolk sac tumor (30%). After treatment with chemotherapy and radiation, repeat imaging demonstrated a right pelvic sidewall mass that decreased in size from 40 mm at 11 months after the initial diagnosis to 18 mm at 22 months after the initial diagnosis. A right pelvis medial thigh wall mass that had a lytic bone component showed a slight increase in size from 151 mm at 11 months after the initial diagnosis to 154 mm at 22 months after the diagnosis. On biopsies performed at 3, 10, and 26 months after the initial diagnosis, this lytic lesion consistently demonstrated a neoplasm composed of low-grade neuroglial differentiation. This is the first case in the medical literature where a residual malignant germ cell tumor consisting of low-grade neuroglial neoplasm is in a site that is not amenable to resection without significant morbidity. The tumor initially regressed with the traditional first-line chemo-radiotherapy regimen but regrew and stabilized with a second regimen of chemotherapy. The clinical course of this case invites consideration for an active surveillance approach in cases with similar characteristics.

Germ cell neoplasms of the testis: Update for 2022

Germ cell neoplasia in situ (GCNIS) is the precursor of both seminomatous and non-seminomatous germ cell tumors. It consists of distended tubules that may have either intratubular seminoma or intratubular embryonal carcinoma cells. Many invasive non-seminomatous tumors contain a mixture of tumor types, which are reviewed here. Morphology, aided by a panel of immunostains, can determine the presence and percent of embryonal carcinoma, yolk sac tumor, choriocarcinoma, or teratoma in such tumors. Use of immunostains, required for diagnosis in perhaps 25% of testicular neoplasms, is reviewed. Changes of classification in the AJCC (8^th edition) in 2016 are discussed, including the partitioning of two tumor types: the central role of chromosome 12p amplification allows both teratoma and yolk sac tumor to be divided into prepubertal types (lacking amplification) and post-pubertal types. Occasionally, sex cord-stromal tumors, hematolymphoid tumors, or epididymal adenomatoid tumors enter the differential diagnosis of germ cell neoplasms.

Testicular Tumors: New Developments in Germ Cell and Sex Cord Stromal Tumors

This article reviews the recent advances and potential future changes in the classification of testicular germ cell and sex cord stromal tumors, highlighting changes in the classification system and terminology with description on newer entities. A discussion on approaching difficult areas and diagnostic pitfalls is also included along with the utility of ancillary investigations. Areas with limited knowledge are highlighted to providing direction for future studies and a bulleted summary in the form of critical care points is provided.

The 2022 World Health Organization Classification of Tumours of the Urinary System and Male Genital Organs-Part A: Renal, Penile, and Testicular Tumours

The fifth edition of the World Health Organization (WHO) classification of urogenital tumours (WHO "Blue Book"), published in 2022, contains significant revisions. This review summarises the most relevant changes for renal, penile, and testicular tumours. In keeping with other volumes in the fifth edition series, the WHO classification of urogenital tumours follows a hierarchical classification and lists tumours by site, category, family, and type. The section "essential and desirable diagnostic criteria" included in the WHO fifth edition represents morphologic diagnostic criteria, combined with immunohistochemistry and relevant molecular tests. The global introduction of massive parallel sequencing will result in a diagnostic shift from morphology to molecular analyses. Therefore, a molecular-driven renal tumour classification has been introduced, taking recent discoveries in renal tumour genomics into account. Such novel molecularly defined epithelial renal tumours include SMARCB1-deficient medullary renal cell carcinoma (RCC), TFEB-altered RCC, Alk-rearranged RCC, and ELOC-mutated RCC. Eosinophilic solid and cystic RCC is a novel morphologically defined RCC entity. The diverse morphologic patterns of penile squamous cell carcinomas are grouped as human papillomavirus (HPV) associated and HPV independent, and there is an attempt to simplify the morphologic classification. A new chapter with tumours of the scrotum has been introduced. The main nomenclature of testicular tumours is retained, including the use of the term "germ cell neoplasia in situ" (GCNIS) for the preneoplastic lesion of most germ cell tumours and division from those not derived from GCNIS. Nomenclature changes include replacement of the term "primitive neuroectodermal tumour" by "embryonic neuroectodermal tumour" to separate these tumours clearly from Ewing sarcoma. The term "carcinoid" has been changed to "neuroendocrine tumour", with most examples in the testis now classified as "prepubertal type testicular neuroendocrine tumour".

An introduction to the WHO 5th edition 2022 classification of testicular tumours

The 5th edition of the World Health Organisation Blue Book was published recently and includes a comprehensive update on testicular tumours. This builds upon the work of the 4th edition, retaining its structure and main nomenclature, including the use of the term 'germ cell neoplasia in situ' (GCNIS) for the pre-invasive lesion of most germ cell tumours and division from those not derived from GCNIS. While there have been important developments in understanding the molecular underpinnings of testicular cancer, this updated classification paradigm and approach remains rooted in morphology. Nomenclature changes include replacement of the term 'primitive neuroectodermal tumour' by 'embryonic neuroectodermal tumour' based on the non-specificity of the former term and to separate these tumours clearly from Ewing sarcoma. Seminoma is placed in a germinoma family of tumours emphasising relation to those tumours at other sites. Criteria for the diagnosis of 'teratoma with somatic transformation' have been modified to not include variable field size assessments. The word 'carcinoid' has been changed to 'neuroendocrine tumour', with most examples in the testis now classified as 'prepubertal type testicular neuroendocrine tumour'. For sex cord-stromal tumours, the use of mitotic counts per high-power field has been changed to per mm2 for malignancy assessments, and the new entities, 'signet ring stromal tumour' and 'myoid gonadal stromal tumour', are defined. Well-differentiated papillary mesothelial tumour has now been defined as tumour type with a favourable prognosis. Sertoliform cystadenoma has been removed as an entity from testicular adnexal tumours and placed with Sertoli cell tumours.

Addressing the diagnostic and therapeutic dilemmas of ovarian immature teratoma: Report from a clinicopathologic consensus conference

Ovarian immature teratoma is a rare subtype of germ cell tumour that can be pure or associated with non-teratomatous germ cell tumour elements and is graded based on extent of the immature neuroectodermal component. Immature teratoma (IT) can also be associated with somatic differentiation in the form of sarcoma, carcinoma, or extensive immature neuroectodermal elements and may produce low levels of serum alpha-fetoprotein. Variable interpretation of these issues underlies diagnostic and management dilemmas, resulting in substantial practice differences between paediatric and adult women with IT. The Malignant Germ Cell International Consortium (MaGIC) convened oncologists, surgeons, and pathologists to address the following crucial clinicopathologic issues related to IT: (1) grading of IT, (2) definition and significance of 'microscopic' yolk sac tumour, (3) transformation to a somatic malignancy, and (4) interpretation of serum tumour biomarkers. This review highlights the discussion, conclusions, and suggested next steps from this clinicopathologic conference.

Somatic-Type Malignancies in Testicular Germ Cell Tumors

The development of somatic-type malignancy (SM) in testicular germ cell tumor represents a major challenge in the diagnosis and treatment of testicular cancer. Most SMs are derived from teratoma, and the remainder is associated with yolk sac tumor. They occur more frequently in metastases than in primary testicular tumors. SMs demonstrate a variety of histologic types, including sarcoma, carcinoma, embryonic-type neuroectodermal tumor, nephroblastoma-like tumor, and hematologic malignancy. Sarcoma, particularly rhabdomyosarcoma, accounts for the majority of SMs in the primary testicular tumors, whereas carcinoma, particularly adenocarcinoma, is the most common SM in metastases. Although SMs derived from testicular germ cell tumors mimic their histologic counterparts in other organs with overlapping immunohistochemical profiles, isochromosome 12p is present in most SMs, which can be useful in the differential diagnosis. The presence of SM in the primary testicular tumor may not worsen the outcome, but the development of SM in metastasis is associated with a poor prognosis. Furthermore, somatic-type carcinoma is likely associated with a worse prognosis than somatic-type sarcoma. Although SMs respond poorly to the cisplatin-based chemotherapy, timely surgical resection is an effective treatment for most patients.

Decoding germ cell tumours for clinicians

PURPOSE OF REVIEW

Germ-cell tumours of the testis affect predominantly younger males aged between 15 and 40 years, with nearly 74,500 new cases estimated globally in 2020. Their rarity and the complex morphology, mean that, in nonexpert hands, there is a significant risk of misdiagnosis of both type and staging of these neoplasms.

RECENT FINDINGS

There have been significant changes in the 2016 WHO classification of Testicular tumours that need to be understood by both pathologists and clinicians for streamlining management. Standardised structured reporting guidelines and discussion at the multidisciplinary-team meetings lead to subsequently better health outcomes and patient safety.

SUMMARY

Therefore, communication with high-quality reports and understanding of clinicians of what constitutes an adequate report, is the key to ensure proper management of these patients. We attempt to discuss the key updates and pathological features that influence management and need to be communicated with clarity and precision.

Germ cell tumors with neuroglial differentiation do not show molecular features akin to their central nervous system counterpart: experience from extra-gynecological sites

Teratomas with secondary somatic malignancy showing neuroglial differentiation (central nervous system (CNS)-type tumors) arising from a glial or neuroepithelial component is a very uncommon event and primarily described in the ovary. We aimed to describe the morphological spectrum and molecular features of CNS type of neuroepithelial tumors arising from the germ cell tumors (GCT) in the extra-gynecological sites. All cases of teratoma and mixed GCT arising from the non-gynecological sites over 7 years were screened for CNS type of neuroepithelial tumors. Detailed histological and immunohistochemical analysis was performed. IDH1 and 2 sequencings were performed in the glial tumors. Fluorescent in situ hybridization (FISH) was performed for EWSR1 rearrangement, 19/19q co-deletion, CDKN2A homozygous deletion, EGFR amplification, and C19MC amplification, wherever required. Out of 302 GCTs examined, the neuroglial tumor was detected in 15 cases. It included nine cases of glial tumors (including one pilocytic astrocytoma (grade I), two diffuse astrocytomas (grade II), one oligodendroglioma (grade II), one gemistocytic astrocytoma (grade II), three anaplastic astrocytomas (grade III), and one case of glioblastoma (grade IV)) and six cases of the embryonal tumor with multilayered rosettes (ETMR). None of the gliomas showed IDH mutation by immunohistochemistry or sequencing. The ETMR cases did not show Lin28 expression or C19MC amplification. To conclude, the spectrum of neuroglial tumors arising from teratoma in the extragonadal sites is vast and most commonly includes glial neoplasms and embryonal tumors. Our findings indicate that the genotype and pathogenesis of tumors with neuroglial differentiation in teratoma are distinct from their CNS counterpart.

NEUROECTODERMAL ELEMENTS ARE PART OF THE MORPHOLOGICAL SPECTRUM OF DICER1-ASSOCIATED NEOPLASMS

Many sarcomas with DICER1 pathogenic variants (PVs) exhibit a characteristic morphology, including a subepithelial layer of malignant mesenchymal cells, areas of rhabdomyoblastic differentiation and cartilaginous and/ or osseous elements. We report 5 DICER1-associated neoplasms (1 moderately to poorly differentiated Sertoli Leydig cell tumour and 4 sarcomas) containing variable amounts of neuroectodermal elements. The neoplasms predominantly involved or were in close proximity to the female genital tract (ovary, uterine corpus, abdominal and pelvic cavity) and occurred in females aged 14 months to 54 years. The neuroectodermal elements were characterised by solid and tubular/ rosette-like patterns and variable immunoreactivity with SALL4 and neuroendocrine markers. In some cases, the neuroectodermal component was focal while in others it was exclusive. In one case, the focal neuroectodermal component within an ovarian Sertoli Leydig cell tumour resulted in extraovarian metastasis. In reporting these cases, we suggest that neuroectodermal elements, including pure neuroectodermal tumours, are part of the morphological spectrum of DICER1-associated neoplasms. It is important that pathologists recognize that a neuroectodermal component (often admixed with other elements) may be a feature of such neoplasms. This will facilitate appropriate tumour and/ or germline testing which could lead to the identification of germline DICER1 PVs (DICER1 syndrome). Three of the patients we report were subsequently shown to have a germline DICER1 PV.

News in the classification of WHO 2022 testicular tumours

The novelties in WHO 5^th edition classification of genitourinary tumours are: a) nomenclature changes, including the replacement of the term "primitive neuroectodermal tumour" with "embryonic-type neuroectodermal tumour" and of "carcinoid" with "neuroendocrine tumour". Also, seminoma is now placed in a "germinoma" family of tumours, while sertoliform cystoadenoma was moved from adnexal tumours to Sertoli cell tumours; b) new entities, specifically signet ring stromal tumour, myoid gonadal stromal tumour and well-differentiated papillary mesothelial tumour.

Somatic-type Malignancies in Testicular Germ Cell Tumors: A Clinicopathologic Study of 63 Cases

The development of somatic-type malignancies (SMs) in testicular germ cell tumors (GCTs) is a rare but well-recognized phenomenon. We studied the pathologic features of 63 GCTs with SMs in the testis (n=22) or metastases (n=41) and correlated these features with clinical outcomes. The patients with SMs in the testis (median age, 26 y) were younger than those with metastatic SMs (median age, 38.5 y). The SMs consisted of carcinomas (n=21), sarcomas (n=21), primitive neuroectodermal tumors (n=15), nephroblastomas (n=3), and mixed tumors (n=3). Sarcoma was the most common SM in the testis (n=11), and most sarcomas were rhabdomyosarcomas (n=9). Carcinoma was the most common SM in metastases (n=20), and most carcinomas were adenocarcinomas (n=12). In metastases, carcinomatous SMs developed after a longer interval from the initial orchiectomy (median times, 213 mo) than sarcomatous SMs (median times, 68 mo). Patients with metastatic SMs had significantly poorer overall survival than those with SMs in the testis (5-y survival rate, 35% vs. 87%; P=0.011). Furthermore, patients with carcinomatous SMs had a significantly worse prognosis than those with sarcomatous or primitive neuroectodermal tumor SMs (5-y survival rates, 17%, 77%, and 73%, respectively; P=0.002), when the whole cohort, including testicular and metastatic SMs, were analyzed. Our results demonstrate that SMs in metastatic GCTs are associated with a significantly worse prognosis than those in the testis. Furthermore, the histologic subtype of SM has a significant effect on the clinical outcome, with the carcinomatous SM carrying the highest risk for mortality.