Immunohistochemistry of germ cell and trophoblastic neoplasms

Pathogenesis and pathobiology of testicular germ cell tumours: a view from a developmental biological perspective with guidelines for pathological diagnostics

Testicular germ cell tumours (GCT) are divided into three different subtypes (types I-III) regarding to their developmental origin, histological differences and molecular features. Type I GCT develop from disturbed primordial germ cells and most commonly occur in children and young adolescents, which is why they are referred to as prepubertal GCT. Type II GCT develop from a non-invasive germ cell neoplasia in situ (GCNIS) and show an isochromosome 12p (i12p) or gain of 12p material as a common and characteristic molecular alteration. Type III GCT originate from distorted postpubertal germ cells (e.g. spermatogonia) in adult patients and have changes on chromosome 9 with amplification of the DMRT1 gene. Type I GCT encompass prepubertal-type teratomas and yolk-sac tumours (YST). Type II GCT include seminoma, embryonal carcinoma, choriocarcinoma, postpubertal-type teratoma and postpubertal-type YST. Types I and II GCT both show similar morphology, but are separated from each other by the detection of a GCNIS and an i12p in type II GCT. For type II GCT it is especially important to detect non-seminomatous elements, as these tumours have a worse biological behaviour and need a different treatment to seminomas. In contrast to types I and II GCT, type III tumours are equivalent to spermatocytic tumours and usually occur in elderly men, with few exceptions in young adults. The development of types I and II GCT seems to depend not upon driver mutations, but rather on changes in the epigenetic landscape. Furthermore, different pluripotency associated factors (e.g. OCT3/4, SOX2, SOX17) play a crucial role in GCT development and can be used as immunohistochemical markers allowing to distinguish the different subtypes from each other in morphologically challenging tissue specimens. Especially in metastatic sites, a morphological and immunohistochemical diagnostic algorithm is important to detect small subpopulations of each non-seminomatous GCT subtype, which are associated with a poorer prognosis and need a different treatment. Furthermore, primary extragonadal GCT of the retroperitoneum or mediastinum develop from misguided germ cells during embryonic development, and might be challenging to detect in small tissue biopsies due to their rarity at corresponding sites. This review article summarises the pathobiological and developmental aspects of the three different types of testicular GCT that can be helpful in the histopathological examination of tumour specimens by pathologists.

Primary germ cell tumours of the mediastinum: A review with emphasis on diagnostic challenges

This article will review current aspects of the histopathological, immunohistochemical and molecular analysis of primary mediastinal germ cell tumours (PMGCTs) as well as their aetiological, epidemiological, clinical and therapeutic features. PMGCTs represent an important differential diagnosis in the spectrum of mediastinal tumours, and their diagnosis is usually made on small tissue samples from core needle biopsies in combination with diagnostic imaging and serum tumour markers. As in lymphomas, a small biopsy is often the only viable tumour sample available from these patients, as they receive chemotherapy prior to eventual surgical resection. Pathologists therefore need to apply an efficient combination of immunohistochemical markers to confirm the diagnosis of a PMGCT and to exclude morphological mimics.

Biomarkers of disease recurrence in stage I testicular germ cell tumours

Stage I testicular cancer is a disease restricted to the testicle. After orchiectomy, patients are considered to be without disease; however, the tumour is prone to relapse in ~4-50% of patients. Current predictive markers of relapse, which are tumour size and invasion to rete testis (in seminoma) or lymphovascular invasion (in non-seminoma), have limited clinical utility and are unable to correctly predict relapse in a substantial proportion of patients. Adjuvant therapeutic strategies based on available biomarkers can lead to overtreatment of 50-85% of patients. Discovery and implementation of novel biomarkers into treatment decision making will help to reduce the burden of adjuvant treatments and improve patient selection for adjuvant therapy.

Primary mediastinal germ cell tumours: an immunohistochemical and molecular diagnostic approach

AIMS

Primary mediastinal germ cell tumours (PMGCTs) are rare mediastinal neoplasms and their diagnosis can be challenging due to small biopsy samples. The aim of this study was to elaborate a diagnostic algorithm using immunohistochemical stainings with focus on novel markers and molecular analysis of isochromosome 12p [i(12p)].

METHODS AND RESULTS

Paraffin-embedded tissues of 32 mediastinal tumours were analysed using immunohistochemical stainings for SALL4, LIN28, OCT3/4, D2-40, CD117, SOX17, SOX2, CD30, ß-hCG, GATA3, FOXA2, GPC3, AFP, TdT, NUT and pan-cytokeratin. Quantitative real-time polymerase chain reaction (qPCR) was performed to investigate i(12p) status. Fifteen seminomas, seven teratomas, one yolk sac tumour, one choriocarcinoma and seven mixed PMGCT were diagnosed. Each entity had different immunohistochemical staining patterns which helped to distinguish them: seminoma (OCT3/4, D2-40, CD117, TdT), embryonal carcinoma (OCT3/4, SOX2), yolk sac tumour (FOXA2, GPC3, AFP) and choriocarcinoma (ß-hCG, GATA3). Mature teratomas stained positive for pan-cytokeratin in epithelial components and focally for SALL4, SOX2, GATA3, D2-40 and FOXA2. Furthermore, a NUT carcinoma mimicking a PMGCT was diagnosed showing a strong nuclear SOX2 and speckled nuclear NUT staining. i(12p) was detected in 24 out of 27 PMGCTs [89%].

CONCLUSION

A diagnostic algorithm is of great importance for a reliable diagnosis of PMGCTs in the usually small tissue biopsy samples. Therefore, a combination of three to four antibodies to identify the correct histological subtype is usually necessary in addition to morphological features. The i(12p) status serves as an additional option to underline germ cell origin in selected cases.

Mediastinal Germ Cell Tumors: A Review and Update on Pathologic, Clinical, and Molecular Features

Mediastinal germ cell tumors (MGCTs) are the most common extragonadal germ cell tumors (GCTs) and most often arise in the anterior mediastinum with a male predilection. MGCTs also have a predilection for patients with Klinefelter syndrome and possibly other genetic conditions. MGCTs, as GCTs at other extragonadal sites, are thought to arise from germ cells improperly retained during migration along the midline during embryogenesis. Similar to their counterparts in the testes, MGCTs are classified into seminomatous and nonseminomatous GCTs. Seminomatous MGCT represents pure seminoma, whereas nonseminomatous MGCTs encompass pure yolk sac tumors, embryonal carcinoma, choriocarcinoma, mature or immature teratoma, and mixed GCTs with any combination of GCT types, including seminoma. Somatic-type or hematologic malignancies can also occur in association with a primary MGCT. MGCTs share molecular findings with GCTs at other sites, most commonly the presence of chromosome 12p gains and isochromosome i(12p). Treatment includes neoadjuvant chemotherapy followed by surgical resection of residual tumor, with the exception of benign teratomas, which require only surgical resection without chemotherapy. In this review, we highlight and provide an update on pathologic, clinical, and molecular features of MGCTs. Immunohistochemical profiles of each tumor type, as well as differential diagnostic considerations, are discussed.

Pattern of placental alkaline phosphatase (PLAP) expression in human tumors: a tissue microarray study on 12,381 tumors

Placental alkaline phosphatase (PLAP) is commonly expressed at high levels in testicular germ cell tumors. PLAP immunohistochemistry (IHC) is thus often used to confirm this diagnosis, especially in cases of putative metastasis. However, other tumors can also express PLAP. To comprehensively determine PLAP expression in normal and tumor tissue, a tissue microarray containing 16,166 samples from 131 different tumor types and subtypes as well as 608 samples from 76 different normal tissue types was analyzed by IHC. Moderate to strong PLAP positivity was found in 27 (21%) of 131 different tumor types including seminoma (96%), embryonal carcinoma (85%), and yolk sac tumors of the testis (56%); endometrioid carcinoma of the endometrium (28%) and the ovary (20%); gastric adenocarcinoma (22%); serous carcinoma (not otherwise specified) of the ovary (17%) and the uterus (11%); adenocarcinoma of the ampulla of Vater (15%); carcinosarcoma of the ovary (11%) and the uterus (8%); esophageal adenocarcinoma (10%); invasive urothelial carcinoma (4%); cholangiocarcinoma (2%); and adenocarcinoma of the lung (1%). Low‐level PLAP immunostaining, often involving only a small fraction of tumor cells, was seen in 21 additional tumor entities. The clinical significance of PLAP expression may vary between tumor types as high PLAP expression was linked to advanced pathological tumor stage (p = 0.0086), nodal metastasis (p = 0.0085), and lymphatic (p = 0.0007) and blood vessel invasion (p = 0.0222) in colorectal cancer, but to low pathological tumor stage in endometrial cancer (p = 0.0043). In conclusion, our data identify several tumor entities that can show PLAP expression at comparable levels to testicular germ cell tumors. These tumor entities need to be considered in cases of PLAP‐positive metastasis. Low‐level PLAP expression can be found in various other tumor entities and should generally not be viewed as a strong argument for germ cell neoplasia.

Report From the International Society of Urological Pathology (ISUP) Consultation Conference on Molecular Pathology of Urogenital Cancers: IV: Current and Future Utilization of Molecular-Genetic Tests for Testicular Germ Cell Tumors

The International Society of Urological Pathology (ISUP) organized a Consultation Conference in March 2019 dealing with applications of molecular pathology in Urogenital Pathology, including testicular tumors (with a focus on germ cell tumors [GCTs]), preceded by a survey among its members to get insight into current practices in testicular germ cell tumor (TGCT) diagnostics and adoption of the ISUP immunohistochemical guidelines published in 2014. On the basis of the premeeting survey, the most commonly used immunomarker panel includes OCT3/4, placental alkaline phosphate, D2-40, SALL4, CD117, and CD30 for GCTs and the documentation of germ cell neoplasia in situ (GCNIS). Molecular testing, specifically 12p copy gain, is informative to distinguish non-GCNIS versus GCNIS related GCTs, and establishing germ cell origin of tumors both in the context of primary and metastatic lesions. Other molecular methodologies currently available but not widely utilized for TGCTs include genome-wide and targeted approaches for specific genetic anomalies, P53 mutations, genomic MDM2 amplification, and detection of the p53 inactivating miR-371a-3p. The latter also holds promise as a serum marker for malignant TGCTs. This manuscript provides an update on the classification of TGCTs, and describes the current and future role of molecular-genetic testing. The following recommendations are made: (1) Presence of GCNIS should be documented in all cases along with extent of spermatogenesis; (2) Immunohistochemical staining is optional in the following scenarios: identification of GCNIS, distinguishing embryonal carcinoma from seminoma, confirming presence of yolk sac tumor and/or choriocarcinoma, and differentiating spermatocytic tumor from potential mimics; (3) Detection of gain of the short arm of chromosome 12 is diagnostic to differentiate between non-GCNIS versus GCNIS related GCTs and supportive to the germ cell origin of both primary and metastatic tumors.

An Algorithmic Immunohistochemical Approach to Define Tumor Type and Assign Site of Origin

Immunohistochemistry represents an indispensable complement to an epidemiology and morphology-driven approach to tumor diagnosis and site of origin assignment. This review reflects the state of my current practice, based on 15-years' experience in Pathology and a deep-dive into the literature, always striving to be better equipped to answer the age old questions, "What is it, and where is it from?" The tables and figures in this manuscript are the ones I "pull up on the computer" when I am teaching at the microscope and turn to myself when I am (frequently) stuck. This field is so exciting because I firmly believe that, through the application of next-generation immunohistochemistry, we can provide better answers than ever before. Specific topics covered in this review include (1) broad tumor classification and associated screening markers; (2) the role of cancer epidemiology in determining pretest probability; (3) broad-spectrum epithelial markers; (4) noncanonical expression of broad tumor class screening markers; (5) a morphologic pattern-based approach to poorly to undifferentiated malignant neoplasms; (6) a morphologic and immunohistochemical approach to define 4 main carcinoma types; (7) CK7/CK20 coordinate expression; (8) added value of semiquantitative immunohistochemical stain assessment; algorithmic immunohistochemical approaches to (9) "garden variety" adenocarcinomas presenting in the liver, (10) large polygonal cell adenocarcinomas, (11) the distinction of primary surface ovarian epithelial tumors with mucinous features from metastasis, (12) tumors presenting at alternative anatomic sites, (13) squamous cell carcinoma versus urothelial carcinoma, and neuroendocrine neoplasms, including (14) the distinction of pheochromocytoma/paraganglioma from well-differentiated neuroendocrine tumor, site of origin assignment in (15) well-differentiated neuroendocrine tumor and (16) poorly differentiated neuroendocrine carcinoma, and (17) the distinction of well-differentiated neuroendocrine tumor G3 from poorly differentiated neuroendocrine carcinoma; it concludes with (18) a discussion of diagnostic considerations in the broad-spectrum keratin/CD45/S-100-"triple-negative" neoplasm.

Metastatic Renal Cell Carcinoma to the Testis: A Clinicopathologic Analysis of Five Cases

The testicular spread of renal cell carcinoma is extremely rare. Five cases of renal cell carcinoma metastatic to the testis are described. The patients ranged from 45 to 81 years of age. Four of the five patients had known renal cell carcinoma. The time intervals between the partial and radical nephrectomies for the primary kidney tumors and the occurrence of testicular metastases ranged from 29 to 34 months. In one patient, the testicular mass was the initial presentation leading to a diagnosis of renal cell carcinoma. There were three ipsilateral metastases, one contralateral metastasis, and one bilateral metastasis. The metastatic deposits ranged in size from 2.0 to 5.7 cm. One case had multiple metastatic tumor nodules. All of the metastatic tumors had clear cell histological features, microscopically concordant with the primary renal cell carcinoma subtype. Three patients died of the disease 17 to 42 months after orchiectomy. One patient is alive with additional metastatic lesions 13 months after orchiectomy. One patient had been free of disease at 87 months after orchiectomy but is now on targeted therapy for an additional metastasis at 93 months after orchiectomy. To date, this report is one of the largest single series of patients with renal cell carcinoma metastatic to the testis, and it has the longest follow-up and survival among all the reported cases.

Serum AFP, hCG and CEA in the Management of Patients with Testicular, Ovarian and Extragonadal Germ Cell Tumors

Serum levels of AFP, hCG and CEA were initially and serially measured in 59 patients with testicular germ cell tumors, and serially in 37 with ovarian and 3 with extragonadal germ cell tumors. Patients with seminoma/dysgerminoma or mature teratoma had normal serum AFP and sporadically slightly elevated hCG. Some patients with embryonal carcinoma, pure or with admixture of seminoma, had serum AFP elevated to maximum 100 U/ml, yet its use for monitoring therapy was limited. Patients with yolk sac tumors had elevated AFP and sometimes CEA levels, those with choriocarcinoma had elevated hCG, and those with compound tumors had one or more of the markers highly elevated. High AFP and/or hCG levels indicated the presence of the relevant tumor cells both in the primary and in residual tumor and/or metastases, also those missed in histological material, and thus were useful in restaging. Unfortunately, their absence in serum did not exclude the presence of marker-negative subpopulations of tumor cells. Changes in marker values paralleled the effects of treatment: the level increasing from any nadir heralded recurrence in patients in remission; elevated or increasing levels during therapy implied resistance to the therapy; decreasing levels indicated regression even though a return to the normal range did not mean eradication of all tumor cells.

Practical Applications of Immunohistochemistry in the Diagnosis of Genitourinary Tumors

Context.—

Pathologic diagnosis of tumors in the genitourinary system can be challenging based on morphology alone, particularly when diagnostic material is limited, such as in core biopsies. Immunohistochemical stain can be a useful tool to aid in the diagnosis.

Objective.—

To provide an update on practical applications and interpretation of immunohistochemical stains in the diagnosis of tumors in prostate, kidney, bladder, and testis. We particularly focus on difficult differential diagnoses, providing our insights in frequently encountered challenging situations. Commonly used immunohistochemical panels are discussed.

Data Sources.—

Review of literature and our own experience.

Conclusion.—

Immunohistochemical stain is a valuable tool in the diagnosis of genitourinary tumors when appropriately used.

Primary mediastinal seminomas: a comprehensive immunohistochemical study with a focus on novel markers

Primary mediastinal seminomas are unusual tumors that can present in a pure form or as part of a mixed germ cell tumor. Contrary to testicular seminomas, little is known about the expression of novel immunohistochemical markers in mediastinal seminomas. This study investigates the immunohistochemical features of these tumors with a focus on novel markers. Thirty-two cases of primary mediastinal seminomas were reviewed; and representative whole-tissue sections were selected for immunohistochemical studies using antibodies directed against high molecular weight cytokeratin 5/6 (CK5/6), low molecular weight cytokeratin (CAM5.2), octamer-binding transcription factor 3/4 (OCT3/4), spalt-like transcription factor 4 (SALL4), GATA binding protein 3 (GATA-3), sry-related HMG box 2 (SOX2), SOX17, human T cell leukemia/lymphoma 1 (TCL1), glypican 3, melanoma associated antigen C2 (MAGEC2), and paired box gene 8 (Pax8). The percentage of positive tumor cells as well as the intensity of staining was evaluated and scored. Thirty-one cases (97%) expressed SOX17, whereas 29 cases (91%) were positive for OCT3/4 and SALL4, respectively. Twenty-eight cases (88%) expressed MAGEC2 and CAM5.2, respectively. Two cases (6%) were positive for Pax8, and a single case (3%) was positive for TCL1. None of the cases stained with CK5/6, GATA-3, SOX2, or glypican 3. Similar to testicular seminomas, mediastinal seminomas show consistent expression of OCT3/4, SALL4, SOX17, and MAGEC2 and are negative for SOX2, glypican 3, GATA-3, and CK5/6. Pax8 positivity is only inconsistently identified in mediastinal seminomas. Contrary to their testicular counterparts, mediastinal tumors show diffuse expression of low-molecular-weight cytokeratin in up to 90% of cases and are commonly negative for TCL1. Although there is some immunohistochemical overlap between testicular and mediastinal seminomas, considerable differences also exist and should be acknowledged when dealing with these tumors.

The Application of Immunohistochemical Biomarkers in Urologic Surgical Pathology

Context

Tumors of the genitourinary tract can be diagnostically challenging, particularly in core biopsies and cystoscopic biopsies with limited material. Immunohistochemistry is a valuable tool to use when morphology alone is insufficient for diagnosis.

Objectives

To review tumors and benign lesions of the kidney, urinary bladder, prostate gland, testis, and paratesticular structures with an emphasis on difficult differential diagnoses, as well as staining patterns in normal tissue. Recommended immunohistochemical stain panels are discussed that can assist in the diagnostic workup.

Data Sources

Review of current literature.

Conclusions

Immunohistochemistry is a valuable tool, assisting in the diagnosis of problematic tumors and benign lesions of the genitourinary tract.

Intratubular spermatocytic seminomas in 2 sprague-dawley rats

This report describes 2 cases of spontaneous intratubular spermatocytic seminomas in Sprague-Dawley rats. These rats were sacrificed at 10 weeks old (case 1) and 40 weeks old (case 2), respectively. Macroscopically, there were no remarkable changes in either case. Microscopically, tumor cells were observed within a single seminiferous tubule (case 1) or several seminiferous tubules (case 2). The proliferating tumor cells were a tripartite cell population comprising small lymphocyte-like, intermediate-sized or large-sized cells, with frequent mitoses, arranged in sheets or forming a basal layer around a tubule or tubules. Immunohistochemically, the tumor cells were strongly positive for proliferating cell nuclear antigen and weakly positive for c-kit, neuron specific enolase and VASA. Our cases provide valuable background control information for the occurrence of seminoma in rats.

Expression of human chorionic gonadotropin in testicular germ cell tumors

BACKGROUND

We have shown that most patients with seminomas have elevated serum concentrations of the free β subunit of human chorionic gonadotropin (hCGβ) and that in nonseminomatous testicular cancer, most of the hCG in the serum is hyperglycosylated (hCG-h). However, the tissue expression of hCG-h or hCGβ in germ cell tumors (GCTs) has not been reported. Our objective was to study the expression and diagnostic value of hCG-h and hCGβ in testicular GCTs.

METHODS

We studied the immunohistochemical expression of hCG, hCG-h, hCGβ, and the free α subunit of hCG (hCGα) in GCTs from 154 patients. We compared the tissue expression with serum concentrations and evaluated the correlation between staining intensity, established prognostic variables, and outcome.

RESULTS

The expression varied between tumor types. All forms of hCG, including hCG-h, were detected in embryonal carcinomas (22%) and mixed GCTs (48%). Polyclonal hCG and monoclonal hCGβ antibodies detected immunoreactivity in some seminomas (7%). No form of hCG was found in spermatocytic seminomas, pure teratomas, or a yolk sac tumor. The serum concentrations correlated with the corresponding tumor expression. The staining intensities of hCG, hCGβ, hCG-h, and hCGα correlated with disease stage but not significantly with relapse, disease-related mortality, or progression-free survival.

CONCLUSION

Trophoblastic tissue expresses hCG, hCG-h, and free subunits together whereas seminoma tissue occasionally expresses hCGβ. This difference might aid in differential diagnosis of some difficult-to-classify cases.

Testicular yolk sac tumor of myxomatous, reticular, and polyvesicular vitelline type in a newborn calf

Yolk sac tumors (YSTs) are rare neoplasms of germ cell origin. In humans, the tumors primarily occur in the testes or ovaries, but occasionally develop at other sites. The neoplastic cells of YSTs form many histological patterns resembling embryonal structures, and the World Health Organization classification lists 11 such patterns: reticular, macrocystic, endodermal sinus, papillary, solid, glandular-alveolar, myxomatous, sarcomatoid, polyvesicular vitelline, hepatoid, and parietal. Among domestic animals, only 2 cases of YST, which were of testicular and abdominal cavity origin, have been reported in calves. In both cases, neoplastic cells had epithelial properties and disseminated metastases in the abdomen. In the present study, the enlarged testis of a newborn calf, which was subsequently diagnosed as YST and exhibited myxomatous, reticular, and polyvesicular vitelline histological patterns, is described. There was no metastasis in this case, and histological and immunohistochemical features varied from previous cases of YST.

Congenital intracranial immature teratoma of the lateral ventricle: a case report and review of the literature

OBJECTIVE

Congenital intracranial tumors are very rare and only account for 0.5-1.5% of all childhood brain tumors. The most common type of these tumors present at birth is teratomas, which represent 0.5% of all intracranial tumors. Most teratomas are midline tumors located predominantly in the sellar and pineal regions. In this study, we report a neonatal intracranial immature teratoma at the lateral ventricle because of its rare location.

CASE REPORT

A 3-day-old female neonate presented with a history of irritability, vomiting, and recurrent generalized clonic seizures since birth. A head computed tomographic scan and magnetic resonance imaging disclosed a large tumor filling the right lateral ventricle and extending into the ipsilateral posterior fossa. With right parieto-occipital craniotomy, large grayish-white lobulated vascular mass was encountered and total removal of tumor was performed. Histological examination revealed the diagnosis of immature teratoma.

CONCLUSION

The prognosis of congenital intracranial immature teratoma is usually poor because the lesions are extensive when they are identified. Prenatal ultrasonography is necessary for the prenatal diagnosis. Fetal magnetic resonance imaging should be made for the evaluation of intracranial tumor. If the tumor is detected before the 24 week of gestation, termination of the pregnancy should be considered.

N-cadherin expression in malignant germ cell tumours of the testis

BACKGROUND

Testicular germ cell tumours (TGCTs) are the most common malignancy in young men aged 18-35 years. They are clinically and histologically subdivided into seminomas and non-seminomas. Cadherins are calcium-dependent transmembrane proteins of the group of adhesion proteins. They play a role in the stabilization of cell-cell contacts, the embryonic morphogenesis, in the maintenance of cell polarity and signal transduction. N-cadherin (CDH2), the neuronal cadherin, stimulates cell-cell contacts during migration and invasion of cells and is able to suppress tumour cell growth.

METHODS

Tumour tissues were acquired from 113 male patients and investigated by immunohistochemistry, as were the three TGCT cell lines NCCIT, NTERA-2 and Tcam2. A monoclonal antibody against N-cadherin was used.

RESULTS

Tumour-free testis and intratubular germ cell neoplasias (unclassified) (IGCNU) strongly expressed N-cadherin within the cytoplasm. In all seminomas investigated, N-cadherin expression displayed a membrane-bound location. In addition, the teratomas and yolk sac tumours investigated also differentially expressed N-cadherin. In contrast, no N-cadherin could be detected in any of the embryonal carcinomas and chorionic carcinomas examined. This expression pattern was also seen in the investigated mixed tumours consisting of seminomas, teratomas, and embryonal carcinoma.

CONCLUSIONS

N-cadherin expression can be used to differentiate embryonal carcinomas and chorionic carcinomas from other histological subtypes of TGCT.

Difficult differential diagnoses in testicular pathology

CONTEXT

Although relatively rare, testicular cancer is the most common solid organ malignancy in young men and remains a leading cause of cancer death in this population. Different types of testicular tumors are treated differently, with an overall very high cure rate with proper management. Pathologists must, therefore, be familiar with important diagnostic pitfalls in testicular pathology, particularly those that result in different treatments or prognoses.

OBJECTIVE

To summarize key diagnostic features and useful ancillary tools for the most frequently encountered problems in testicular tumor pathology.

DATA SOURCES

Current texts, PubMed (National Library of Medicine) articles, and archives at Indiana University School of Medicine and Beth Israel Deaconess Medical Center were all reviewed.

CONCLUSIONS

Problematic differential diagnoses include seminoma versus nonseminomatous germ cell tumors, germ cell tumors versus non-germ cell tumors, intratubular germ cell neoplasia versus atypical germ cells with maturation arrest, pseudolymphovascular invasion versus real lymphovascular invasion in germ cell tumors, and macroscopic Sertoli cell nodules versus Sertoli cell tumors. In almost all cases, awareness of the differential diagnostic possibilities based on routine light microscopic features permits application of either additional, directed observations or immunohistochemical studies that lead to an accurate diagnosis.

Primary mediastinal "thymic" seminomas

Over the last half century, our knowledge on germ cell tumors (GCT) has increased dramatically. Tumors that at one time were supposed to originate exclusively from certain anatomic areas are now thought to occur in ubiquitous distribution. Nevertheless, because of their similar histopathologic features, the conventional classic evaluation of these patients will require careful clinical history as well as complete physical and radiologic evaluation. The emphasis in this manuscript will be to highlight the occurrence and overall characteristics of one of the most common GCTs in the mediastinal region-seminoma. A more detailed discussion of mediastinal GCTs is well beyond the scope of this review.

Role of biochemical markers in testicular cancer: diagnosis, staging, and surveillance

Testis cancer is one of the few solid organ malignancies for which reliable serum tumor markers are available to help guide disease management. Human chorionic gonadotropin, alpha fetoprotein, and lactate dehydrogenase play crucial roles in diagnosis, staging, prognosis, monitoring treatment response, and surveillance of seminomatous and nonseminomatous germ cell tumors. Herein we discuss the clinical applications of germ cell tumor markers, the limitations of these markers in the management of this disease, and additional serum molecules that have been identified with potential roles as novel germ cell tumor markers.

A simple method for the immunocytochemical detection of proteins inside nuclear structures that are inaccessible to specific antibodies

It has been demonstrated elsewhere that a high concentration of an antigen within the nucleolus may prevent its proper recognition by specific antibodies. In this study, the authors found that a short proteinase treatment allowed for the detection of antigens in the nucleoli. The described approach is compatible with the simultaneous observation of proteins fused to fluorescent tags and with preembedding electron microscopy. It appears that the described method can be useful in situations when the proper recognition of antigens by specific antibodies is disturbed by a high density of cellular structures or a high concentration of antigens inside these structures.

Yolk sac tumor of the thyroid gland: a case report

Extragonadal yolk sac tumors are uncommon and usually seen in sacrococcygeal, mediastinal, intracranial, and retroperitoneal sites. Yolk sac tumors of the head and neck region are rare, and the few reported cases have arisen in neonates or infants in conjunction with a teratoma or other germ cell tumor subtypes. We report a unique case of a pure yolk sac tumor presenting as a primary lesion in the right thyroid lobe of a 10-year-old girl. The diagnosis was suspected after fine-needle aspiration, and extensive sampling of the thyroidectomy specimen revealed no teratoma or other germ cell tumor. Serum α-fetoprotein levels were markedly elevated 6 days after excision, and imaging disclosed numerous bilateral pulmonary nodules suggestive of metastatic disease but did not reveal a mediastinal mass. The tumor has shown a favorable response to bleomycin, etoposide, and cisplatin chemotherapy. To the best of our knowledge, this is the 1st description of a primary pure yolk sac tumor of the thyroid.

Pituitary choriocarcinoma in an adolescent male: tumor-derived CG and GH delay diagnosis

BACKGROUND

Primary intracranial germ cell tumors usually present in the first two decades of life, often with precocious puberty. The most common location is in the pineal gland; suprasellar germ cell tumors are rare. We present an additional case of a suprasellar choriocarcinoma producing GH, and review the literature.

CASE

This French Canadian, 17 year-old male presented to the ER with a history of mild weight loss and an episode of syncope while hiking in Mexico, but with no other neurological symptoms. Puberty began at age 13 years (growth spurt: 15-16 years), and he attained an adult height within genetic target by age 16 years. Past medical history was negative except for myopia diagnosed during childhood. System review revealed increased thirst and nocturia. The mother was treated for an oligo-astrocytoma in 2007. Clinical examination showed a euthyroid, well-looking young man with 20 ml testicles. Endocrine evaluation revealed elevated testosterone, mildly elevated PRL, borderline low FT4, and decreased IGF-I, morning cortisol and urine osmolality; tumor markers were positive in serum and CSF (hCG>50 IU/L, AFP>10 ng/mL). A transphenoidal biopsy of a 4.5 cm, homogeneous, non-calcified, suprasellar mass was compatible with the diagnosis of choriocarcinoma and stained intensely for hCG and hGH, presumably the placental variant (GH-V) as previously found in vitro in choriocarcinoma cell lines. Combined chemotherapy and irradiation led to tumor regression and undetectable serum hCG to 36 months of follow-up. He is doing well with no evidence of tumor progression and is on complete hormone replacement therapy.

CONCLUSIONS

Choriocarcinomas can have a hormonal profile that delays the development of symptoms, due to hCG stimulation of both the gonadal and thyroid axes. This report corroborates previous in vitro evidence that choriocarcinoma cells are able to make GH-V. To what extent the patient's tumor-derived GH contributed to his normal growth is not known. Prognosis for this intracranial neoplasm is very reserved, although combined radiotherapy and chemotherapy has been successful in our patient now 36 months post-diagnosis.

Embryonal carcinoma in the abdominal cavity of a male calf

An embryonal carcinoma was diagnosed in the abdominal cavity of a 55-day-old male calf. Macroscopically, a large volume of ascitic fluid was observed along with white to yellowish-white masses of various sizes densely located on the abdominal wall and the surface of abdominal organs. There was an absence of testes in the scrotum. Histologically, the tumor cells were polygonal, and the tumor was mostly composed of sheets of densely packed solid patterns with occasional papillary and tubular structures. Cell nuclei were variable in size, and cellular mitotic rate was high. Immunohistochemically, tumor cells were positive for alpha-fetoprotein, placental alkaline phosphatase, cytokeratin, and carcinoembryonic antigen. Ultrastructurally, the tumor cells had large nuclei, extensive rough endoplasmic reticulum, and small numbers of mitochondria. Microvillus-like structures and desmosomes were occasionally observed. From lectin histochemical examination, the tumor cells were positive for concanavalin A, wheat germ agglutinin, peanut agglutinin, Dolichos biflorus agglutinin, soybean agglutinin, Griffonia simplicifolia I, and Bauhinia purpurea, and negative for Ulex europaeus agglutinin I. Results of histopathological, immunohistochemical, and ultrastructural examinations of the tumor were similar to those obtained for human embryonal carcinoma.

Oxygenomics in environmental stress

Environmental stressors such as chemicals and physical agents induce various oxidative stresses and affect human health. To elucidate their underlying mechanisms, etiology and risk, analyses of gene expression signatures in environmental stress-induced human diseases, including neuronal disorders, cancer and diabetes, are crucially important. Recent studies have clarified oxidative stress-induced signaling pathways in human and experimental animals. These pathways are classifiable into several categories: reactive oxygen species (ROS) metabolism and antioxidant defenses, p53 pathway signaling, nitric oxide (NO) signaling pathway, hypoxia signaling, transforming growth factor (TGF)-beta bone morphogenetic protein (BMP) signaling, tumor necrosis factor (TNF) ligand-receptor signaling, and mitochondrial function. This review describes the gene expression signatures through which environmental stressors induce oxidative stress and regulate signal transduction pathways in rodent and human tissues.

Canine classical seminoma: a specific malignant type with human classifications is highly correlated with tumor angiogenesis

Background

Human seminoma is classified as classical seminoma (SE) and spermatocytic seminoma (SS). Human SE is known to be more malignant and metastasizing more frequently than SS. Tumor angiogenesis is highly related with tumor progression and metastasis, with microvessel density (MVD) being an important parameter of metastatic potential. Canine seminoma is not yet well-established as SE or SS type including correlation with angiogenesis. We classified canine SE and SS, and then compared them to tumor associated vessels.

Methods

Twenty-three cases of canine seminomas (2 intratubular, 9 diffuse, and 12 intratubular/diffuse seminomas showing both intratubular and diffuse patterns) were classified as SE or SS by immunohistochemistry (IHC) using monoclonal antibody against PLAP and by PAS stain. The histopathological data were then compared to see if there was a correlation with SE or SS. Angiogenesis of seminomas were evaluated by immunohistochemical assay using polyclonal antibody against Von Willebrand factor (vWF) and by calculating the means of MVD, vessels area and perimeters using computerized image analysis. Statistical Package for Social Sciences (SPSS) program was used for various statistical analyses.

Results

The numbers of PLAP+/PAS+ canine SEs were 8/23 (34.8%) and PLAP-/PAS- SSs were 15/23 (61.2%). All SE cases (8/8, 100%) were intratubular/diffuse types. SS types included 2 intratubular (2/15, 13.3%), 9 diffuse (9/15, 60%), and 4 intratubular/diffuse (4/15, 26.7%) types. MVD and vascular parameters in SEs were significantly higher than in SSs, showing the highest value in the intratubular/diffuse type. Seminomas observed with neoplastic cells invasion of vessels presented higher perimeter and area values than seminomas without conformed neoplastic cells invasion.

Conclusion

In this study, we demonstrated a positive relationship between canine SE and tumor angiogenesis. Furthermore, we also showed that a tumor cells invasion of vessels were a correlated vascular parameter. Although metastasis of canine seminomas has rarely been reported, our results support that canine SE could have high metastatic potential similar to the human counterpart. Further studies are required to clarify the relationship between canine SE and clinical data with metastatic factors.

Diagnostic utility of SALL4 in extragonadal yolk sac tumors: an immunohistochemical study of 59 cases with comparison to placental-like alkaline phosphatase, alpha-fetoprotein, and glypican-3

Extragonadal yolk sac tumors (YSTs; primary and metastatic) are rare but are malignant germ cell tumors. Pathologic diagnosis of extragonadal YSTs can be challenging without immunohistochemical markers but markers used for diagnosing these tumors such as placental-like alkaline phosphatase (PLAP), alpha-fetoprotein (AFP), and glypican-3 lack adequate sensitivity and/or specificity. In earlier studies with gonadal germ cell tumors, SALL4 has been identified as a novel diagnostic marker for YSTs and other types of primitive germ cell tumors. Here, we investigated the diagnostic utility of SALL4 in 59 extragonadal YSTs (27 primary sacrococcygeal, 15 primary nonsacrococcygeal, and 17 metastatic) by immunohistochemical staining. We also compared SALL4 with PLAP, AFP, and glypican-3. In addition, we performed immunostains for pancytokeratin, epithelial membrane antigen, and OCT4 in these tumors. Our results showed that all 59 YSTs showed strong pancytokeratin staining (70% tumor cells in 1 case, >90% tumor cells in 58) and 10 (17%) of them also showed focal epithelial membrane antigen staining (<3% tumor cells). All 59 YSTs were negative for OCT4. Strong SALL4 staining was seen in all 59 YSTs (in more than 90% tumor cells in 54 and 70% to 85% tumor cells in 5 YSTs). Only 39 of 59 (66%) YSTs showed positive PLAP staining and the staining was often focal (in less than 30% tumor cells) (28 of 39 cases). Positive AFP staining was seen in the vast majority of YSTs (56 of 59 or 95%); however, 32 (54%) YSTs showed staining in less than 30% tumor cells. Although all 59 YSTs showed positive glypican-3 staining, 18 (30%) showed staining in less than 30% tumor cells, and additional 10 (17%) showed staining in between 30% and 60% tumor cells. In these 59 YSTs, the mean percentage of tumor cells stained with PLAP was 14% (range: 0% to 90%), with AFP 35% (range 0% to 95%), and with glypican-3 57% (range: 1% to 100%), whereas the mean percentage of tumor cells stained for SALL4 was 94% (range: 70% to 100%) (P<0.001). Our results indicate that SALL4 is a novel sensitive (100% sensitivity) diagnostic marker for extragonadal YSTs. SALL4 is a more sensitive marker than PLAP, AFP, or glypican-3 for extragonadal YSTs.

Cytology of head and neck squamous cell carcinoma variants

The most common diagnosis rendered with head and neck fine needle aspiration (FNA) biopsy is metastatic squamous cell carcinoma (SCC). While most cases of metastatic SCC pose little diagnostic difficulty, the diagnosis of metastatic histologic variants of SCC, often coupled with less common etiologies, can be more problematic. This manuscript reviews the clinicopathologic features of the histologic variants of upper aerodigestive tract SCC (verrucous, papillary, spindle cell, undifferentiated, acantholytic, and basaloid) and uncommon etiologies of head and neck SCC (human papillomavirus, Epstein-Barr Virus, and NUT midline carcinomas). Particular attention is paid to the cytologic features of these lesions. Differential diagnoses and the use of ancillary testing are discussed.

The unusual presentation of gastric adenocarcinoma as a testicular mass: a favorable response to docetaxel and Cisplatin plus oral tegafur/uracil and leucovorin

Gastric cancer is one of the most common malignancies in the world. The routes of metastasis include direct extension, lymphatics, and peritoneal or hematogenous spread. Testicular metastasis is rare. We present here a 23-year-old gastric cancer patient who first presented with right-side testis swelling and pain. Diagnosis of metastatic adenocarcinoma was made after right-side orchiectomy. Gastric adenocarcinoma with ascites and peritoneal seeding was found after esophagogastroscopy and abdominal computed tomography. The patient received chemotherapy consisting of docetaxel 36 mg/m(2) and cisplatin 30 mg/m(2) on day 1 and day 8, plus oral tegafur/uracil 300 mg/m(2)/day and leucovorin 90 mg/day on day 1 to day 14 in a 21-day cycle, and he had a partial response to the chemotherapy. Metastatic tumors, especially gastric adenocarcinoma, should be considered in the differential diagnosis of patients presenting with testicular mass and they may respond well to chemotherapy.

SALL4 is a novel sensitive and specific marker for metastatic germ cell tumors, with particular utility in detection of metastatic yolk sac tumors

BACKGROUND

The correct diagnosis of metastatic germ cell tumors is critical, because these tumors can be effectively treated and are even cured with modern therapy. Their histopathologic diagnosis can be challenging without immunohistochemical markers, which currently have limitations. SALL4 is a novel stem cell marker essential to maintain pluripotency and self-renewal of embryonic stem cells. In the current study, the authors investigated the utility of SALL4 as a potential diagnostic marker for metastatic germ cell tumors.

METHODS

Ninety metastatic germ cell tumors from testis, ovary, and extragonadal sites were stained with a monoclonal SALL4 antibody. In addition, 170 metastatic nongerm cell malignancies, including 158 carcinomas (6 head and neck, 8 thyroid, 12 lung, 8 breast, 7 hepatocellular, 3 cholangiocarcinomas, 2 ampullary, 10 pancreatic, 18 gastric, 15 esophageal, 10 renal cell, 10 urothelial, 12 prostatic, 18 ovarian, 6 uterine, and 13 colonic) and 12 melanomas, were also stained to test SALL4 specificity.

RESULTS

All 22 seminomas, 7 dysgerminomas, 22 embryonal carcinomas, and 14 of 15 yolk sac tumors displayed strong and diffuse SALL positivity in >90% of tumor cells (80% of tumor cells were strongly positive in the remaining yolk sac tumor). Five of 7 choriocarcinomas and 9 of 18 teratomas were also variably positive for SALL4. In contrast, only 10 (esophageal, gastric, and colonic adenocarcinomas) of 170 metastatic somatic tumors demonstrated focally weak SALL4 reactivity (<25% tumor cells).

CONCLUSIONS

SALL4 is a novel sensitive and highly specific marker for metastatic germ cell tumors, and is particularly useful for detecting metastatic yolk sac tumors.

SALL4 is a novel sensitive and specific marker of ovarian primitive germ cell tumors and is particularly useful in distinguishing yolk sac tumor from clear cell carcinoma

Ovarian primitive germ cell tumors (GCTs) are uncommon tumors and sometimes pose diagnostic challenges. Among them, yolk sac tumor (YST) poses the greatest diagnostic difficulty and can be mistaken for clear cell carcinoma (CCC). Current immunohistochemical markers such as alpha-fetoprotein (AFP), glypican-3, cytokeratin (CK) 7, and epithelial membrane antigen (EMA) used to distinguish YST from CCC lack adequate sensitivity and specificity. Here by immunohistochemistry, we investigated a novel marker SALL4 in 98 GCTs (29 YSTs, 18 dysgerminomas, 6 gonadoblastomas, 6 embryonal carcinomas, 15 immature and 12 mature teratomas, 7 carcinoid tumors, 3 strumal carcinoids, and 2 struma ovarii) with particular interest of exploring SALL4 to distinguish YST from CCC. One hundred sixty-three non-GCTs including 45 CCCs were also stained. We found that SALL4 is strongly positive in more than 90% tumor cells in all YSTs, dysgerminomas, gonadoblastomas, and embryonal carcinomas. Variable SALL4 staining is seen in 11 of 15 immature teratomas. All other GCTs included in this study are negative for SALL4. Except 3 CCCs with focal SALL4 staining (<15% tumor cells), SALL4 is negative in the remaining 160 non-GCTs. We also compared SALL4 with AFP, glypican-3, CK7, and EMA in all YSTs and CCCs. AFP and glypican-3 are positive in 24 (83%) and 20 (69%) YSTs, respectively, whereas 16 (35%) and 13(28%) CCCs show positive AFP and glypican-3 staining, respectively. Three (10%) and 4 (14%) YSTs show focal (<2% tumor cells) CK7 and EMA staining, respectively. CK7 and EMA are positive in all 45 CCCs but 3 (7%) and 1 (2%) cases show staining in less than 30% tumor cells, respectively. Our findings indicate that SALL4 is a novel sensitive and specific marker for ovarian primitive GCTs. SALL4 is particularly useful in distinguishing YST from CCC and better than AFP, glypican-3, CK7, and EMA.

Clinical Management of Ovarian Small-Cell Carcinoma of the Hypercalcemic Type: A Proposal for Conservative Surgery in an Advanced Stage of Disease

Ovarian small-cell carcinoma of the hypercalcemic type is a rare and highly malignant tumor. In two thirds of the patients, the tumor is associated with asymptomatic paraneoplastic hypercalcemia. The diagnosis may be impeded; the tumor must be distinguished from other tumors with similar features.

This tumor occurs predominantly in young women and is merely lethal. The 1-year survival is solely 50%, with an overall 5-year survival rate of approximately 10%. It is believed that the empirical treatment characterized by combination of radical surgery, chemotherapy, and radiotherapy results in the most favorable outcome in terms of survival. However, the outcome remains extremely poor despite this aggressive approach.

Alternatively, these poor survival rates may justify a less aggressive fertility sparing approach without compromising the outcome. Such an approach is illustrated by a case report involving a patient with ovarian small-cell carcinoma of the hypercalcemic type, FIGO stage IIIC. A fertility-sparing approach was used, consisting of conservative surgery followed by induction chemotherapy, interval debulking surgery, and local radiotherapy. During follow-up of 60 months, there was no evidence of disease and the normal menstrual cycle resumed.

In addition to this case report, histopathological features, different therapeutic modalities, and outcome of ovarian small-cell carcinoma of the hypercalcemic type is reviewed. This report suggests that a fertility-sparing approach may be just as feasible as the generally applied aggressive approach.

Spinal intradural primary germ cell tumour--review of literature and case report

BACKGROUND

Primary spinal cord germ cell tumour is a rare tumour. We herein review the tumour characteristics, associated risk factors, treatment policy, and patterns of failure of primary intradural germ cell tumour.

METHOD

We conducted a PUBMED search using a combination of keywords such as "spinal germ cell tumor," "germinoma," "extradural," "intradural," "intramedullary," "extramedullary," and identified 19 cases of primary spinal germ cell tumour. Clinical features, pathologic characteristics, and treatment details of these patients including status at follow-up were noted from respective case reports. We also describe a case of a young Indian patient of intradural extramedullary germ cell tumour treated with a combination of surgery, chemotherapy, and radiotherapy.

FINDINGS

The median age at presentation was 24 years. The most common location of the tumour was thoracic (40%). Beta-HCG overproduction was noted in 40% of the patients. Most patients were treated with a combination of surgery, radiation therapy, and systemic chemotherapy. Median follow-up was 16.5 months. Recurrence was observed in 10% of the patients, all in beta-HCG over-producing tumours. The illustrative case was a 28-year male, presenting with pain in lower back and both lower limbs for 2 months. Magnetic resonance imaging spine showed an inhomogeneous hyperintense soft tissue mass at L(2)-L(4) spinal level. He was treated with complete surgical excision and four cycles of chemotherapy with BEP regimen following a histological diagnosis of non-seminomatous germ cell tumour. Palliative irradiation to the lumbar spine was given on progression at 3 months. The patient eventually succumbed to his condition, due to compressive transverse myelitis possibly due to cervical cord metastasis.

CONCLUSION

Limited surgery followed by upfront radiation therapy and adjuvant chemotherapy is the optimal management of this rare group of tumour. Omission of radiation therapy from the treatment armamentarium might engender local recurrence and spinal dissemination at first failure.

[Gastrointestinal adenocarcinomas with a choriocarcinomatous component: 2 cases and a review of 120 cases in the literature]

Gastrointestinal adenocarcinoma with a choriocarcinomatous component (GACC) is an extremely rare and highly malignant human chorionic gonadotrophin-producing neoplasm. The development of this tumour from dedifferentiation or trans-differentiation of adenocarcinomatous cells is the most likely mechanism. 102 of the 120 cases reviewed in the literature presented enough clinicopathological information to be analysed. This tumour can be purely choriocarcinomatous or associated with an adenocarcinoma as in half of the observations. It is usually found in the stomach although it may be found throughout the digestive tract. The diagnosis of GACC should only be retained after having clearly eliminated a metastasis from a choriocarcinoma in particular in the gonads. The prognosis is very poor in particular in the gastric forms of this disease, with death observed within 12 months following diagnosis in 2/3 of the patients. There is no treatment consensus, and it is decided on a case-by-case basis.