Mixed germ cell sex cord–stromal tumors of the testis and ovary. Morphological, immunohistochemical, and molecular genetic study of seven cases

Histological and immunohistochemical characterization of 17 gonadal tumours in koi carp (Cyprinus carpio koi)

Reports on abdominal tumours in koi carp are scarce and most are from the gonads. Their histological diagnosis is challenging due to the occurrence of mixed populations of neoplastic cells and the few availability of cross-reactive antibodies in fish tissues. The present study aims to provide a histopathological characterization of seventeen gonadal tumours, enriched by a wide antibody panel (vimentin, CD117, placental alkaline phosphatase-PLAP, AE1/AE3 cytokeratin, E-cadherin, proliferating cell nuclear antigen-PCNA, müllerian-inhibiting substance-MIS, GATA4 and Inhibin-α) applied on whole and tissue microarray (TMA) sections. Abdominal enlargement was associated with tumours filling 30%-80% of the abdominal cavity; frequently, the gonads had been completely replaced by neoplastic tissue. Twelve cases were characterized as sex cord-stromal tumours (SCSTs), three as germ cell tumours (GCTs), one as mixed germ cell sex cord-stromal tumour (MGCSCST) and one as carcinoma. By immunohistochemistry, PLAP enabled confirmation of GCTs, ovarian carcinoma and the objective identification of a further cell component in 8 out of the 12 SCSTs that were reclassified as mixed tumours. The use of an immunohistochemical panel can help in refining the histological diagnosis, but the morphological diagnosis still represents the main tool for the characterization of these tumours in koi carp.

Mixed germ cell-sex cord stromal tumour of the testis and ovary: comparison and contrast

Mixed germ cell-sex cord stromal tumours (MGC-SCSTs) of the testis and ovary differ significantly in their histological appearance, clinical behaviour, and molecular genetics. Until recently, the germ cells of testicular MGC-SCST were considered to be invariably histologically bland, whereas those from neoplasms that arise in the ovary have histological features characteristic of premalignancy. However, a recent histological and molecular genetic study demonstrated histological abnormalities and multiple chromosomal losses and gains in a small subset of testicular cases, thus providing the first evidence that testicular MGC-SCSTs can exceptionally show histological and molecular abnormalities. All cases of testicular MGC-SCST reported to date have been clinically benign, whereas ovarian examples are sometimes the precursor of a malignant germ cell neoplasm that can be clinically aggressive. Both genetic and epigenetic influences likely account for dissimilarities in these uncommon gonadal neoplasms.

Gonadoblastoma versus ovarian mixed germ cell-sex cord stromal tumor in women or girls with no evidence of a disorder of sex development: A problem in differential diagnosis

Gonadoblastoma occurring in a normal girl or woman has been confused with ovarian mixed germ cell-sex cord stromal tumor (MGC-SCST) due to a lack of knowledge that the former occurs occasionally in a normal woman or girl. In this article, we develop histological criteria that facilitate the distinction of gonadoblastoma in an individual with a normal karyotype and no evidence of a disorder of sex development from ovarian MGC-SCST. We reviewed the histological findings of gonadoblastoma occurring in normal individuals and compared them to cases of ovarian MGC-SCST in our files. The histological findings of gonadoblastoma differ substantially from those of ovarian MGC-SCST. Importantly, gonadoblastoma contains two types of transformed germ cells, some histologically benign and others premalignant, whereas MGC-SCST contains only a single type, typically premalignant in the ovary and benign in the testis. Furthermore, degenerative changes of hyalinization and calcification are common in gonadoblastoma, whereas they are extremely rare in MGC-SCST. Although the great majority of cases of gonadoblastoma occur in an individual with a disorder of sex development and an abnormal karyotype, a substantial number arise in a normal woman or girl with no evidence of a disorder of sex development. In the latter circumstance, it is important to distinguish gonadoblastoma from ovarian MGC-SCST. It is very likely that those gonadoblastomas arising in a normal individual develop through a different molecular pathway than the ones that occur in the dysgenetic gonads of an individual with a disorder of sex development.

Novel insights into the mixed germ cell-sex cord stromal tumor of the testis: detection of chromosomal aneuploidy and further morphological evidence supporting the neoplastic nature of the germ cell component

The existence of a true mixed germ cell-sex cord stromal tumor (MGSCT) of the testis remains controversial. Based on our experience with rare testicular tumors in this spectrum, we sought to perform a detailed clinicopathologic and molecular study of MGCSCT. Eight cases of testicular MGSCT were morphologically reviewed, screened for chromosomal aberrations (using array comparative genomic hybridization (aCGH) and low pass genomic sequencing), and analyzed by next generation sequencing (The Illumina TruSight Tumor 170). Immunohistochemistry for OCT3/4, Nanog, SALL4, DMRT1, and inhibin was performed on the cohort. Clinical data and follow-up were assessed by medical record review. All patients were karyotypically normal men aged 27-74 years (median 41). All tumors had a similar biphasic morphology characterized by various proportions of the sex cord component resembling granulosa cell tumor of adult type and the germ cell component cytomorphologically akin to spermatocytic tumor. Germ cells were haphazardly scattered throughout the tumor or arranged in larger groups, without tubular formation. In 4 cases, atypical mitoses were found within the germ cells. Additionally, in 2 cases there was invasion into the spermatic cord, adjacent hilar soft tissue and into the tumor capsule, which contained both tumor components. Immunohistochemically, focal nuclear expression of DMRT1 was found in the germ cell component in 7/7 analyzable tumors, while SALL4 was positive in 6 cases and negative in one case. All tumors were negative with OCT3/4 and Nanog. The sex cord stromal component had immunoreactivity for inhibin in 7/7 analyzable cases. Four of 8 cases were cytogenetically analyzable: 4/8 by low pass genomic sequencing and 2/8 by aCGH. The results of both methods correlated well, revealing mostly multiple chromosomal losses and gains. One case revealed loss of chromosome 21; 1 case had loss of chromosomes 21 and 22 and partial gain of 22; 1 case had loss of chromosomes 22 and Y, partial loss of X, and gain of chromosomes 20, 5, 8, 9, 12, and 13; and the remaining one gain of chromosomes 20, 3, 6, 8, 2x(9), 11, 2x(12), 13, 14, 18, and 19. Three cases were analyzable by NGS; clinically significant activating mutations of either FGFR3 or HRAS were not detected in any case. Follow-up was available for 4 patients (12, 24, 84, and 288 months) and was uneventful in all 4 cases. The identification of extratesticular invasion of both the germ cell and sex cord stromal components, the DMRT1 expression, and the presence of atypical mitoses in germ cells argue for the neoplastic nature of the germ cell component. The molecular genetic study revealing multiple chromosomal losses and gains in a subset of the cases provides the first evidence that molecular abnormalities occur in testicular MGSCT. Multiple chromosomal aneuploidies, namely, recurrent losses of chromosomes 21 and 22 and gains of 8, 9, 12, 13, and 20, indicate that the germ cell component might be related to the morphologically similar spermatocytic tumor, which is characterized by extensive aneuploidies including recurrent gains of chromosomes 9 and 20 and loss of chromosome 7. In summary, our data support that rare examples of true MGSCT of the testis do exist and they represent a distinct tumor entity with admixed adult-type granulosa cell tumor and spermatocytic tumor components.

Identification of a Novel Zebrafish Mutant Line that Develops Testicular Germ Cell Tumors

Testicular tumors are the most common solid malignant tumors in men 20-35 years of age. Although most of testicular tumors are curable, current treatments still fail in 15%-20% of patients. However, insufficient understanding of the molecular basis and lack of animal models limit development of more effective treatments. This study reports the identification of a novel zebrafish mutant line, ns1402, which develops testicular germ cell tumors (TGCTs). While both male and female ns1402 mutants were fertile at young age, male ns1402 mutants became infertile as early as 9 months of age. This infertility was associated with progressive loss of mature sperm. Failure of spermatogenesis was, at least in part, explained by progressive loss of mature Leydig cells, a source of testosterone that is essential for spermatogenesis. Interestingly, TGCTs in ns1402 mutants contained a large number of Sertoli cells and gene expression profiles of Sertoli cells were altered before loss of mature Leydig cells. This suggests that changes in Sertoli cell properties happened first, followed by loss of mature Leydig cells and failure of spermatogenesis. Taken together, this study emphasizes the importance of cell-cell interactions and cell signaling in the testis for spermatogenesis and tissue homeostasis.

Protein expression of the transcription factors DMRT1, TCLF5, and OCT4 in selected germ cell neoplasms of the testis

In the present study, we investigated protein expression of the transcription factors mammalian doublesex and mab-3 related transcription factor 1 (DMRT1), basic helix-loop-helix transcription factor-like 5 (TCLF5), and octamer-binding transcription factor 4 (OCT4) in normal human spermatogenesis, testicular mixed germ cell-sex cord stromal tumor (MGC-SCST), spermatocytic tumor, and seminoma. In normal human spermatogenesis, DMRT1 is expressed in the nuclei of spermatogonia but not in those of more mature germ cells. By way of contrast, TCLF5 is expressed in the nuclei of some clusters of primary spermatocytes that have entered meiosis 1, in secondary spermatocytes, and in round (early) spermatids in the seminiferous tubules of adults during the reproductive years. OCT4 is expressed in primordial germ cells but not in the seminiferous tubules of the normal adult testis during the reproductive years. DMRT1 is expressed in the germ cells of both testicular MGC-SCST and spermatocytic tumor, whereas TCLF5 is not expressed in either neoplasm. These low-grade neoplasms, however, differ histologically in that all the germ cell nuclei of testicular MGC-SCST resemble spermatogonia, whereas in spermatocytic tumor, the nuclei of the medium-sized and large cells resemble those of primary spermatocytes. Both neoplasms lack expression of OCT4. By way of contrast, in seminoma, a fully malignant testicular germ cell tumor, the germ cell nuclei express OCT4 but do not express either DMRT1 or TCLF5.

Spermatogonial Nature of the Germ Cell Component of Canine Testicular Mixed Germ Cell-Sex Cord Stromal Tumours

The present study has characterized the germ cell component of canine testicular mixed germ cell-sex cord stromal tumours (MGSCTs) by examining the histological nature and histochemical and immunohistochemical features using gonocytic and spermatogonial cellular markers, c-Kit, placental alkaline phosphatase (PLAP), protein gene product 9.5 (PGP9.5), Sal-like protein 4 (SALL4), and the periodic acid-Schiff (PAS) reaction. Histologically, all 45 examples of MGSCTs were classified as spermatocytic seminomas (SSs) and Sertoli cell tumours in combination. The germ cell component of all MGSCTs was negative by PAS staining. Immunohistochemically, PLAP immunoreactivity was lacking in the germ cell component of all MGSCTs, which is not consistent with a gonocytic origin. The germ cell component was positive for PGP9.5 and SALL4 in all MGSCTs and positive for c-Kit in 53% of MGSCTs, which is consistent with the phenotype of spermatogonia. Furthermore, the germ cell component in 71% of MGSCTs had moderate immunoreactivity for SALL4, which is suggestive of a spermatogonial phenotype. Conversely, 29% of cases had a minor population of germ cells showing strong SALL4 immunoreactivity, suggesting a phenotype similar to prespermatogonia. The results suggest that the germ cell component of canine MGSCTs is morphologically classified as SS, with the majority of cases showing the spermatogonial phenotype and some cases containing a small population of prespermatogonia.

The 2016 WHO Classification of Tumours of the Urinary System and Male Genital Organs-Part A: Renal, Penile, and Testicular Tumours

The fourth edition of the World Health Organization (WHO) classification of urogenital tumours (WHO "blue book"), published in 2016, contains significant revisions. These revisions were performed after consideration by a large international group of pathologists with special expertise in this area. A subgroup of these persons met at the WHO Consensus Conference in Zurich, Switzerland, in 2015 to finalize the revisions. This review summarizes the most significant differences between the newly published classification and the prior version for renal, penile, and testicular tumours. Newly recognized epithelial renal tumours are hereditary leiomyomatosis and renal cell carcinoma (RCC) syndrome-associated RCC, succinate dehydrogenase-deficient RCC, tubulocystic RCC, acquired cystic disease-associated RCC, and clear cell papillary RCC. The WHO/International Society of Urological Pathology renal tumour grading system was recommended, and the definition of renal papillary adenoma was modified. The new WHO classification of penile squamous cell carcinomas is based on the presence of human papillomavirus and defines histologic subtypes accordingly. Germ cell neoplasia in situ (GCNIS) of the testis is the WHO-recommended term for precursor lesions of invasive germ cell tumours, and testicular germ cell tumours are now separated into two fundamentally different groups: those derived from GCNIS and those unrelated to GCNIS. Spermatocytic seminoma has been designated as a spermatocytic tumour and placed within the group of non-GCNIS-related tumours in the 2016 WHO classification.

PATIENT SUMMARY

The 2016 World Health Organization (WHO) classification contains new renal tumour entities. The classification of penile squamous cell carcinomas is based on the presence of human papillomavirus. Germ cell neoplasia in situ of the testis is the WHO-recommended term for precursor lesions of invasive germ cell tumours.

Mixed testicular neoplasia in a short beaked common dolphin Delphinus delphis

A diagnosis of mixed testicular neoplasia in a short beaked common dolphin Delphinus delphis involving a Sertoli cell tumor, an interstitial (Leydig) cell tumor and a seminoma is presented. Lymphatic spread of the Sertoli cell tumor to an adjacent retroperitoneal lymph node was observed. Testicular neoplasms have been infrequently reported in marine mammals. Demonstration of clinical signs and further health implications is extremely challenging when dealing with non accessible wildlife species, such as dolphins. However, metastatic potential for these neoplastic conditions should be considered.

Comparison of morphological, immunohistochemical, and molecular genetic features of inflammatory fibroid polyps (Vanek's tumors)

Vanek's tumor (inflammatory fibroid polyp) is a rare benign lesion occurring throughout the digestive tract. Histologically, two patterns can be recognized. Classical Vanek's tumor contains concentric formations of proliferating spindle cells which are CD34 positive. Atypical, inflammatory pseudotumor-like Vanek's tumor lacks concentric formations and is CD34 negative. Recently, mutations in platelet-derived growth factor receptor alpha (PDGFRA) were reported in gastric and small intestinal Vanek's tumors. In this study, KIT exons 9, 11, 13, and 17, PDGFRA exons 12, 14, and 18, and a part of exon 15 BRAF for point mutation V600E were screened in 23 cases of Vanek's tumor, both classical (n = 16) and inflammatory pseudotumor-like (n = 7). No mutations in all analyzed exons of KIT and BRAF and in exon 14 of PDGFRA were detected. Six Vanek's tumors harbored activating mutations in PDGFRA exons 12 (n = 5) and 18 (n = 1) respectively: S566_E571delinsK (n = 1), S566_E571delinsR (n = 4), and D842 del (n = 1). The mutations were detected in the classical (n = 5), as well as inflammatory pseudotumor-like (n = 1) Vanek's tumors. The results of this study suggest that the two morphological patterns of Vanek's tumor more probably represent only variants of one type of tumor than two different lesions. Furthermore, BRAF mutations were not shown to drive growth of PDGFRA wild-type Vanek's tumors.

Primitive small cell tumor with epithelial, gangliocytic, neuroendocrine, and mesenchymal differentiation: report of 2 cases

The authors describe 2 tumors that, to the best of their knowledge, are hitherto undescribed. The predominant cell type was small round to fusiform dark blue cells. The dark blue cells formed distinct epithelial cords with gland-like formations with mucicarmine-positive mucus. Another distinctive component of the tumors was a mesenchymal one. The mesenchymal areas appeared benign and could be likened to a fibroma having a densely collagenous stroma, or they had spindle cells set in the myxoid background, rendering a myxoma-like appearance. Another distinctive feature was ganglion cell differentiation. Mitotic figures, including atypical forms, were found only in the small cell component. All cells were immunohistochemically negative for actin, calponin, desmin, HMB45, neurofilament protein, CD99/MIC2, Melan A, tyrosinase, serotonin, CD56, Melan A, GFAP, and S-100 protein. Cytokeratin, synaptophysin, FLI1 protein, and chromogranin antibodies reacted only in the primitive small round cells, while all the other components were cytokeratin negative. Fluorescence in situ hybridization showed that the tumors are without the EWSR1 gene translocation and gain 12p. Ultrastructurally, the cells were endowed with well-formed intercellular desmosomes membrane-bound secretory in the cytoplasm. Granules were found in the cytoplasm. We suggest the name "primitive small cell tumor with epithelial, gangliocytic, neuroendocrine, and mesenchymal differentiation" for this neoplasm.

Prenatal development of murine gonads with special reference to germ cell differentiation: a morphological and immunohistochemical study

The prenatal differentiation of male and female gonads of the mouse was investigated both morphologically and immunohistochemically. Sexual dimorphism could be detected as early as 12 days post-coitum (dpc) by the appearance of the primary elements of the tunica albuginea and positive immunoreactivity for anti-Muellerian hormone in the Sertoli cells of the male gonad. Male germ cells passed two waves of mitotic activity, a first wave between 12 and 14 dpc, which is followed by apoptosis of the old germ cell generation, and a second wave between 17 and 20 dpc. Oct-4 was expressed as a juxtanuclear ring in the cytoplasm of germ cells up to 17 dpc. Subsequently, it was down-regulated and completely disappeared in 20 dpc full-term fetuses. By contrast, M2A antigen revealed only a weak immunoreaction in some germ cells of 14 dpc gonads, but exhibited strong signals in all germ cells of 20 dpc full-term fetuses. Therefore, we postulate that, in the mouse, prenatal germ cells represent two populations: the first is immunopositive for Oct-4 and disappeared in full-term fetuses, whereas the second appeared in 14 dpc and is immunopositive for M2A antigen.

Recent Advances in the Pathology and Classification of Gonadal Neoplasms Composed of Germ Cells and Sex Cord Derivatives

In recent years, our understanding of neoplasms composed of germ cells and sex cord derivatives has increased. In this review, advances in the classification and pathology of ovarian germ cell-sex cord-stromal tumors are discussed. Only 2 neoplasms, each with a distinctive pathogenesis and clinicopathologic features, are included in this category. Gonadoblastoma is a tumor that usually occurs in the dysgenetic gonads of intersex patients that have a Y chromosome, whereas mixed germ cell-sex cord-stromal tumor arises in normal gonads in patients without sex chromosomal abnormalities. Ovarian mixed germ cell-sex cord-stromal tumors differ from their testicular counterparts in their histological appearance, immunohistochemical staining reactions, and biological behavior probably because the latter show a greater degree of maturity of their germ cell component. The introduction of cisplatin-based chemotherapy and the application of tumor markers have dramatically improved the clinical outlook for those patients who develop secondary malignant germ cell neoplasms.

Diagnostic morphological features of PDGFRA-mutated gastrointestinal stromal tumors: molecular genetic and histologic analysis of 60 cases of gastric gastrointestinal stromal tumors

In this study, 60 gastrointestinal stromal tumors of the stomach were analyzed to elucidate the possible relation of their morphology to the mutation status of KIT and PDGFRA genes. The patients included 27 men and 33 women with a mean age of 63.8 years (range, 12-92 years). Only 1 tumor occurred before the age of 21 years. KIT mutations were detected in 31 cases (51.7%), PDGFRA mutations in 22 cases (36.7%), and 7 cases (11.7%) were KIT and PDGFRA wild type. When the mutation status was correlated with histologic features of the tumors, epithelioid or mixed epithelioid/spindle cell pattern and mast cell infiltration were found as the most reliable signs of PDGFRA mutation. Neoplastic rhabdoid cells and multinucleated giant cells, also previously reported as features of PDGFRA-mutated gastrointestinal stromal tumors, seemed to be less specific but still helpful markers in our study. Finally, tumor-infiltrating lymphocytes and myxoid stroma do not seem to be valuable histologic signs.