Half-life of serum alpha-fetoprotein in prepubertal testicular yolk sac tumors: an index significantly associated with prognosis.

PURPOSE: To evaluate the association between serum alpha-fetoprotein (AFP) half-life (HL) and prognosis in prepubertal children with elevated AFP values 3 to 4 weeks after surgery for testicular yolk sac tumors (YST). METHODS: Prepubertal patients with testicular YST treated with radical orchiectomy between January 2016 and December 2022 were retrospectively reviewed. Negative outcomes were defined as relapse, metastasis or death. Univariate and multivariate logistic regression analyses were conducted to select risk factors for negative outcomes. RESULTS: A total of 42 patients were eventually enrolled into the study. Patients were divided into non-negative and negative outcomes groups, consisting of 35 and 7 patients, respectively. Thirty-five patients were stage I, two cases were stage II, and five cases were stage IV, according to the Children's Oncology Group staging system. The overall survival (OS) rate was 100%. Average AFP values significantly decreased after resection (P < 0.001). A significant positive correlation was shown between pre- and postoperative AFP values (r = 0.60, P < 0.001). Long AFP HL was considered as an independent risk factor for negative outcomes in YST patients underwent radical orchiectomy (P = 0.04). The cut-off value for AFP HL was 5.78 days, regardless of age division. CONCLUSION: Testicular YST is a relatively rare disease in children with an OS of 100%, and salvage chemotherapy is effective even in grade IV patients. The postoperative AFP HL was significantly associated with prognosis in prepubertal patients with testicular YST. The cut-off value for AFP HL is 5.78 days regardless of the effect of physiological AFP elevation.

Beta-Catenin Alterations in Postchemotherapy Yolk Sac Tumor, Postpubertal-Type With Enteroblastic Features.

Postchemotherapy postpubertal-type yolk sac tumors (YST) with glandular and solid phenotypes are aggressive and commonly resistant to systemic chemotherapy. These neoplasms show morphologic features that significantly overlap with those of somatic carcinomas with "enteroblastic" or "fetal" phenotype (the preferred terminology depends on the site of origin). They often present as late or very late recurrences, and their diagnosis is challenging because they frequently affect patients in an age group at risk for carcinomas of somatic origin. Recently, we incidentally identified examples of postchemotherapy glandular and solid YST with "enteroblastic" phenotypes and nuclear expression of beta-catenin, prompting us to further evaluate the prevalence of this phenomenon. We found nuclear expression of beta-catenin in 10 (29%) of 34 such tumors. A subset of cases with nuclear beta-catenin expression was further analyzed with a DNA sequencing panel (n = 6) and fluorescence in situ hybridization for isochromosome 12p [i(12p); n = 5]. Sequencing identified exon 3 CTNNB1 variants in 3 (50%) of 6 analyzed cases, and fluorescence in situ hybridization was positive for i(12p) in 5 of 5 cases. In conclusion, a significant subset of postchemotherapy YST with glandular or solid architecture and "enteroblastic" phenotype demonstrates beta-catenin alterations, suggesting that activation of Wnt signaling may play a role in the progression of these neoplasms. Moreover, nuclear beta-catenin expression in these tumors represents a potential diagnostic pitfall given that carcinomas of true somatic origin with overlapping morphology may also be positive for this marker.

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.

Yolk Sac Differentiation in Endometrial Carcinoma: Incidence and Clinicopathologic Features of Somatically Derived Yolk Sac Tumors Versus Carcinomas With Nonspecific Immunoexpression of Yolk Sac Markers.

Endometrial somatically derived yolk sac tumors are characterized by yolk sac morphology with AFP, SALL-4, and/or Glypican-3 immunoexpression. Yolk sac marker expression, however, is not limited to tumors with overt yolk sac histology. Three hundred consecutive endometrial malignancies were assessed for immunomarkers of yolk sac differentiation. Of these, 9% expressed ≥1 yolk sac marker, including 29% of high-grade tumors. Only 3 (1%) met morphologic criteria for yolk sac differentiation; these were originally diagnosed as serous, high-grade NOS, and dedifferentiated carcinoma. Two were MMR-intact and comprised exclusively of yolk sac elements, while the dedifferentiated case was MMR deficient and had a background low-grade endometrioid carcinoma; this case also showed BRG1 loss. All 3 were INI1 intact. Nonspecific yolk sac marker expression was seen in 14 carcinosarcomas, 4 endometrioid, 2 serous, 1 clear cell, 1 dedifferentiated, 1 mixed serous/clear cell, and 1 mesonephric-like carcinoma. INI1 was intact in all cases; one showed BRG1 loss. Twenty were MMR-intact, and 4 were MMR deficient. All MMR-deficient cases with yolk sac marker expression, both with and without true yolk sac morphology, had no evidence of residual disease on follow-up, whereas 82% of MMR-intact cases developed recurrent/metastatic disease. In summary, endometrial somatically derived yolk sac tumors were rare but under-recognized. While AFP immunostaining was specific for this diagnosis, Glypican-3 and SALL-4 expression was seen in a variety of other high-grade carcinomas. INI1 loss was not associated with yolk sac morphology or immunomarker expression in the endometrium, and BRG1 loss was rare. All patients with MMR-deficient carcinomas with yolk sac immunoexpression +/- morphology were disease-free on follow-up, whereas the majority of MMR-intact cancers showed aggressive disease.

Survival difference among adult and pediatric mediastinal yolk sac tumors cases: A meta-analysis of case reports.

BACKGROUND: Mediastinal Yolk sac tumors (YST) are rare and highly malignant extragonadal germ cell tumors with rapid growth and early metastases. We sought to conduct a meta-analysis of published case reports/case series to compare differences in survival, demographics, and treatment modalities between adult and pediatric patients with YST. METHODS: Ovid Embase, Cochrane, and Ovid Medline databases were searched for primary mediastinal pure YST cases. The primary outcome was overall survival (OS). Log-rank and Cox regression were used. This study is registered on PROSPERO (CRD42022367586). RESULTS: Among 846 studies, 87 met our inclusion criteria including 130 patients (Adults: 90 and Pediatrics: 40). About 41.5% of the patients were from the United States. The median age was 23.0 (Q1-Q3: 17.0-30.0), 88.5% were males, and (32.3%) were Asian. Stage II represented almost 40%. AFP was elevated in 96.9%. Respiratory distress was the presenting symptom in 65.4%. Chemotherapy, radiotherapy, and surgery were utilized in 84.6, 23.1, and 64.7% respectively. Median OS was 24 months (Adults: 23 months, Pediatrics: 25 months, P = 0.89). 3- and 5-year OS were 34.4% and 22.9% in adults and 41.5% and 41.5% in pediatrics, respectively. On multivariate analysis, anterior location of tumors, receipt of chemotherapy, and undergoing surgery were associated with better OS. CONCLUSION: Primary mediastinal YSTs are rare, but lethal neoplasms. Our meta-analysis showed that mediastinal YSTs mimic other non-seminomatous mediastinal GCTs in terms of clinical characteristics and available treatment options. Early diagnosis, neoadjuvant chemotherapy, and surgical resection are the key points for effective management and improved outcomes.

Testicular Mixed Teratoma and Yolk Sac Tumor, Prepubertal Type: A Case Report with Summary of Prior Published Cases.

BACKGROUND: Testicular mixed germ cell tumor is common in the post-pubertal age, less so in prepuberty. There are only 3 reports of prepubertal mixed teratoma and yolk sac tumor. Two of these cases had immature teratoma component and were in the neonatal age group. The third case in a toddler had a mature teratoma component. CASE REPORT: An 18-month-old boy presented with a testicular mass. Serum AFP was elevated (2200 ng/ml). The orchidectomy specimen contained a yolk-sac tumor and a small epidermoid cyst, indicating a mature teratomatous component. CONCLUSION: We report a testicular mixed teratoma and yolk sac tumor, prepubertal type along with summary of prior published cases. There is only one report describing this combination of mature teratoma with yolk sac tumor in the prepubertal testis.

Analysis of GATA3 and FOXA2 expression suggests that downregulation of genes involved in the maintenance of a mature yolk sac tumor phenotype may underlie sarcomatoid transformation.

In the post-chemotherapy setting, germ cell tumors of the testis (GCTT) that resemble non-specific sarcomas and co-express cytokeratins and glypican-3 (GPC3) are diagnosed as "sarcomatoid yolk sac tumor postpubertal-type (YSTpt)". The diagnosis of sarcomatoid YSTpt is clinically relevant but challenging due to its rarity, non-specific histology, and negative α-fetoprotein (AFP) staining. Recently, FOXA2 has emerged as a key-gene in the reprogramming of GCTT (activating the transcription of several genes, among which GATA3), and immunohistochemical studies showed that GATA3 and FOXA2 have a higher sensitivity for non-sarcomatoid YSTpt than GPC3 and AFP. We found that sarcomatoid YSTpt did not express FOXA2 [0: 14/14 (100%)] and showed focal expression of GATA3 [0: 12/14 (85.7%), 1 + : 2/14 (14.3%)], thus suggesting that these markers are not useful in diagnosing this tumor. Furthermore, we proposed a potential mechanism of sarcomatoid transformation in the post-chemotherapy setting of GCTT, mediated by the downregulation of FOXA2 and GATA3.

Retroperitoneal yolk sac tumour encroaching the liver and adrenal gland with tumour thrombus in cavo-atrial region and hepatic veins.

Paediatric germ cell tumours (GCT) are rare tumours and are unique because of varied clinical presentation and locations. Yolk sac tumour is the predominant malignant histology and a serum marker; alpha fetoprotein is used to see treatment response and recurrent disease. It is extremely rare to find a retroperitoneal GCT with tumour thrombus extending up to the cavo-atrial region with involvement of the hepatic veins. We report a case of retroperitoneal yolk sac tumour (RPYST) with extension to the liver and right adrenal gland along with tumour thrombus in the inferior vena cava and in the right and middle hepatic veins. The child was operated after satisfactory response to chemotherapy. Excision of the tumour along with the right adrenal gland and around 5 cm of retro-hepatic caval resection was done. Inferior vena cava resection was tolerated without reconstruction. Currently child is disease-free and symptom-free at 22 months of follow-up with normal serum marker.

Survival outcomes and establishment of a novel risk stratification system in patients with ovarian yolk sac tumors.

OBJECTIVE: To evaluate the survival outcomes and establish a risk stratification system in patients with ovarian yolk sac tumors (OYST). METHODS: The recurrence-free survival (RFS), disease-specific survival (DSS), and prognostic factors were retrospectively evaluated in 151 OYST patients treated in our hospital between 2006 and 2022. A risk stratification system based on the identified prognostic factors was established. RESULTS: The median follow-up time was 5.1 years, with a 5-year RFS and DSS rate of 75.5% and 91.2%, respectively. FIGO stage III-IV and the interval between treatment and normalization of AFP were two prognostic predictors. Significant differences in RFS and DSS (both P < 0.001) were identified between patients who had normalized AFP ≤ 3 and ≥ 4 cycles of chemotherapy, or among patients who had normalized AFP after ≤2, 3-4, and ≥ 5 cycles of chemotherapy. FIGO stage I - II and stage III-IV were scored as 0 and 2, respectively. AFP normalization ≤2, 3, 4, and ≥ 5 cycles of chemotherapy were scored as 0, 1, 2, and 4, respectively. A total score of 0-1, 2-3, and ≥ 4 were stratified patients into low-risk (96 patients), intermediate-risk (35 patients), and high-risk groups (20 patients), respectively. Patients in three risk stratifications manifested significant differences in both RFS and DSS (P < 0.0001). CONCLUSION: This risk stratification system based on tumor stage and the interval between treatment and normalization of AFP may help to guide clinical management by dividing OYST patients into three risk groups.

Yolk Sac Tumour Arising in the Glans Penis an Achondroplasic Child: A Case Report with Summary of Prior Published Cases.

BACKGROUND: Yolk sac tumors (YST) are commonly encountered gonadal germ cell tumors in children, especially in the prepubertal age group. In addition to gonadal primary, it can occur in multiple extragonadal sites, of which sacrococcygeal, retroperitoneum, gastric and mediastinum are the commonest. There are 4 previous reports of primary penile YST. CASE REPORT: We describe a primary penile yolk sac tumor in a child with achondroplasia. CONCLUSION: Yolk sac tumor can occur in the penis during the prepubertal period. Penile yolk sac tumor associated with achondroplasia has not been previously reported, but this could be incidental.

Detailed characterization of PD-1/PD-L1 and CTLA4 expression and tumor-infiltrating lymphocytes in yolk sac tumors.

BACKGROUND: Immune checkpoint blockade (ICB) is considered as a promising approach for cancer treatment. However, the potency of ICB therapy in yolk sac tumors (YSTs) has not been confirmed, and the comprehensive analysis of tumor immune microenvironment and the expression of PD-1/PD-L1 and CTLA4 were also not thoroughly evaluated. METHODS: Immunohistochemistry was performed in formalin-fixed, paraffin-embedded tumor specimens from 23 YSTs patients to detect the density and distribution of tumor-infiltrating T cells, tertiary lymphoid structures (TLSs), as well as the expression of PD-1/PD-L1 and CTLA4. RESULTS: Overall, more than half (61 %) of all patients exhibited an immune-desert phenotype based on CD3+ T cells. PD-1 expression was identified in five tumor samples (21.7 %), and PD-L1 expression exhibited a different positive rate in tumor cells (TCs) and tumor-infiltrating lymphocytes (TILs) (39.1 % and 17.4 %). Noteworthily, the rate of positive CTLA4 expression in both TCs and TILs was markedly higher (69.6 % and 56.5 %) than those of PD-1 and PD-L1 expression. Furthermore, TLSs were observed in 21.74 % of all tissues, and samples with TLSs exhibited significantly higher densities of TILs and higher expression of immune checkpoint molecules, particularly PD-1/PD-L1. In addition, tumors located in testes also exhibited a higher density of TILs and higher expression of immune checkpoint molecules. CONCLUSION: Generally a high frequency of CTLA4 expression was found, PD-1/PD-L1 expression, the immune-inflamed phenotype, and TLSs were low frequency in YSTs, however, YSTs in testes showed a higher density of TILs and higher expression of immune checkpoint molecules.

FoxA2 is a reliable marker for the diagnosis of yolk sac tumour postpubertal-type.

AIMS: Yolk sac tumour postpubertal-type (YSTpt) shows a wide range of histological patterns and is challenging to diagnose. Recently, forkhead box transcription factor A2 (FoxA2) emerged as a driver of YSTpt formation and a promising marker for diagnosing YSTpt. However, FoxA2 has not been tested in the different patterns of YSTpt. This study aimed to assess the staining pattern of FoxA2 in te different patterns of YSTpt and other germ cell tumours of the testis (GCTT), comparing it with glypican-3 (GPC3) and α-fetoprotein (AFP). METHODS AND RESULTS: FOXA2, GPC3 and AFP immunohistochemistry was performed on 24 YSTpt (24 microcystic/reticular, 10 myxoid, two macrocystic, five glandular/alveolar, two endodermal sinus/perivascular, four solid, two polyembryoma/embryoid body and two polyvesicular vitelline) and 81 other GCTT. The percentage of positive cells (0, 1+, 2+, 3+) and the intensity (0, 1, 2, 3) were evaluated regardless of and within each YSTpt pattern. FoxA2 was positive in all YSTpt (24 of 24) and all but one (23 of 24) exhibited 2+/3+ stain, with higher intensity [median value (mv): 2.6] than AFP (1.8) and GPC3 (2.5). Both FoxA2 and GPC3 were positive in all microcystic/reticular (24 of 24), myxoid (10 of 10), macrocystic (two of two), endodermal sinus/perivascular (four of four) and polyembryoma/embryoid body (two of two) patterns. Nevertheless, only FoxA2 was positive in all glandular/alveolar (five of five), solid (four of four) and polyvesicular vitelline (two of two) patterns. The intensity of FoxA2 was higher than AFP and GPC3 in almost all YST patterns. In the other GCTT, FoxA2 was positive only in teratoma postpubertal-type (Tpt) [13 of 20 (65%)], with staining almost exclusively confined to the mature gastrointestinal/respiratory tract epithelium. CONCLUSIONS: FoxA2 is a highly sensitive and specific biomarker that supports the diagnosis of YSTpt. FoxA2 is superior to GPC3 and AFP, especially in rare and difficult-to-diagnose histological patterns of YSTpt, but mature glands of Tpt could represent a potential diagnostic pitfall.