The temporary anatomical structures prominent in the first trimester may be fulfilling exchange functions assigned to the placenta in the second and third trimester

The extra-embryonic coelom (EEC) and secondary yolk sac areprominent structures in the gestational sac during the firsttrimester of human pregnancy, at a time before the definitiveplacental circulation becomes established. We propose that theEEC and yolk sac play a critical role in the nutrition of earlypregnancy, fulfilling exchange functions which are assumed bythe placenta at a later stage.     

Ovarian hepatoid yolk sac tumours: morphological, immunohistochemical and ultrastructural features

AIM: The clinicopathological, immunohistochemical and ultrastructural features of two ovarian hepatoid yolk sac tumours (H-YST) from our files are reviewed. METHODS AND RESULTS: Using avidin-biotin-peroxidase complex technique, the immunoprofile of these tumours was compared to that of a classic yolk sac tumour and to that previously reported for hepatocellular carcinomas. The clinicopathological and morphological features of our cases are similar to the seven previously reported ovarian cases. This rare germ cell tumour occurs in young females (mean age = 17.6 years) and presents most commonly with abdominal pain and a large ovarian mass (average size = 140 mm). Histologically, the tumours display a striking resemblance to hepatocellular carcinoma. The absence of an associated typical pattern of yolk sac tumour or other germ cell neoplasm may make it difficult to recognize the germ cell origin of this lesion. Our cases demonstrated positive staining for alpha-fetoprotein and alpha-1-antitrypsin. In addition, there was immunoreactivity with polyclonal carcinoembryonic antigen (CEA) antiserum in a canalicular pattern, focal staining for inhibin, oestrogen and progesterone receptors and absence of immunoreactivity for CK7 that contrasts with the immunophenotype of a usual yolk sac tumour. CONCLUSIONS: Ovarian H-YST and hepatocellular carcinoma share a similar immunoprofile. Ovarian H-YST is a highly aggressive tumour, most patients exhibit recurrence or die of disease within 2 years of diagnosis.     

原发性性腺外卵黄囊瘤40例临床病理分析

目的：探讨原发性性腺外卵黄囊瘤( extragonadal yolk sac tumor, eYST)的临床病理特征、组织来源、形态学特点、免疫表型及鉴别诊断。方法回顾性分析40例原发性eYST的临床病理资料、形态学和免疫表型特征,结合文献对其临床病理特点进行分析。结果40例eYST中男性24例、女性16例,年龄6个月~42岁,平均12岁,≥12岁者17例,占42.5%。肿瘤分别位于纵隔16例(40.0%)、骶尾12例(30.0%)、腹膜后5例(12.5%)、松果体4例(10.0%)、阴道3例(7.5%)。40例患者中32例为纯YST(80.0%),8例(20.0%)含有1~2种其他类型的生殖细胞肿瘤(germ cell tumor, GCT)成分。结论原发性eYST少见,纵隔和骶尾是eYST最常见的解剖部位;发生在纵隔的肿瘤患者大部分限于成年男性,患者平均年龄明显大于骶尾、腹膜后、松果体和阴道肿瘤的患者(P<0.05),发生在其他部位的eYST多限于青春期前的儿童;一些成人eYST的病例包含其他类型的GCT成分,儿童eYST总是为纯YST;eYST表现出多形性的组织学特征,结合免疫表型对明确诊断、鉴别诊断有一定价值。     

Ovarian yolk sac tumor with virilization during pregnancy: immunohistochemical demonstration of Leydig cells as functioning stroma

A case is reported of yolk sac tumor occurring in the left ovary and complicated by pregnancy. The 22-year-old patient presented at 28 weeks gestation with virilization and elevated serum levels of testosterone and alpha-fetoprotein. The tumor showed the typical features of yolk sac tumor with a mixture of islands of Leydig cells. The accumulations of Leydig cells were well demarcated from the cellular components of the yolk sac tumor and were distributed throughout the tumor, although with predominant localization at the periphery. By immunohistochemistry the Leydig cells were intensely positive for vimentin and negative for cytokeratins, allowing clear distinction from the cell components of the yolk sac tumor, which were positive for cytokeratins and negative for vimentin. Testosterone was also identified in the cytoplasm of the Leydig cells. After tumor resection the testosterone and alpha-fetoprotein levels declined simultaneously; this, together with the immunohistochemical demonstration of testosterone, indicates that the Leydig cells were responsible for the endocrine manifestations. Furthermore, antibodies against inhibin alpha-subunit and calretinin could be used to detect the Leydig cells. The present case, a combination of yolk sac tumor and Leydig cells acting as a functioning stroma and causing virilization during pregnancy, is very rare.     

Gastric cancer with choriocarcinoma and yolk sac tumor components: case report

Choriocarcinoma- and yolk sac tumor-like differentiation have rarely been reported in gastric cancers. We report a case of gastric adenocarcinoma, concurrently possessing choriocarcinoma and yolk sac tumor components, of a 74-year-old man. A hemorrhagic, 11 × 8 × 3 cm, tumor with ulceration was located in the body and pre-pylorus of the stomach. Histological examination of the resected specimens demonstrated intermingled proliferation of three different components, namely, adenocarcinoma, choriocarcinoma and yolk sac tumor, which were immunoreactive for carcinoembryonic antigen (CEA), beta-subunit of human chorionic gonadotropin (HCG) and alpha-fetoprotein (AFP), respectively. Gastric cancers with germ cell tumor components are uncommon and this is the second reported case of gastric cancer with choriocarcinoma and yolk sac tumor components.     

First trimester uterine, placental and yolk sac haemodynamics in pre-eclampsia and preterm labour

BACKGROUND: We hypothesized that impaired trophoblast invasion leads to umbilicoplacental blood flow disturbances that could be detected by Doppler ultrasonography during the first trimester of the pregnancy. METHODS: After successful fresh IVF or ICSI programme, 41 of 47 enrolled subjects were followed up every 1-2 weeks between weeks 6 and 11 of gestation. Ten patients who later developed pre-eclampsia and/or preterm labour formed the study group and the control group consisted of 31 uncomplicated IVF/ICSI pregnancies. Doppler parameters of uterine, spiral, intraplacental, chorionic, umbilical and yolk sac haemodynamics were assessed. RESULTS: At the week 8, the study group demonstrated higher (P < 0.05) maternal intraplacental resistance indices (RI) than the control group. A week later, yolk sac artery RI and umbilical artery mean velocity (V(mean)) in the study group were lower (P < 0.05) compared to the control group. In late first trimester, increased (P < 0.01) velocities and RI were observed in chorionic arteries of the study group. During early pregnancy, no difference in uterine and spiral artery haemodynamics and in umbilical artery pulsatility index (PI) values was observed between the groups. CONCLUSIONS: Uterine and spiral artery RI and umbilical artery PI are unable to detect placental vascular disturbances during early pregnancy. Elevated intraplacental RI indicates increased maternal intraplacental impedance as early as week 8 of gestation. Decreased yolk sac artery RI and umbilical artery V(mean) in the study group at week 9 of gestation were speculated to indicate hampered transition of blood supply from yolk sac to umbilical circulation, underlining the emphasized role of yolk sac function for the maintenance of pregnancy.     

Escape of the yolk sac: a hypothesis to explain the embryogenesis of gastroschisis

Gastroschisis is a significant birth defect that in many countries has shown an increased prevalence in recent decades, and the change has affected primarily younger mothers. Despite numerous epidemiological studies no other consistent associated risk factor has been identified. In this paper we review the five main theories related to the pathogenesis of this malformation and outline the reasons why we think none fully explains the embryogenesis of gastroschisis. We briefly present some clinical observations we have made that we consider germane to the pathogenesis and outline a hypothesis that we think can account for the origins of this malformation. Our proposal is that the determining defect in gastroschisis is failure of the yolk sac and related vitelline structures to be incorporated into the umbilical stalk. Otherwise, ventral closure of the lateral abdominal walls occurs normally, thus orphaning the vitelline duct and yolk sac outside both the main body stalk and the abdominal wall. Thus, in addition to the umbilicus, the abdominal wall has a separate perforation through which the midpoint of the gut is attached to the exteriorized vitelline structures. This connection through the ventral wall prevents normal egress of the gut into the umbilical cord during the second month of development and acts as the egress point for the gut resulting in gastroschisis.     

Rat visceral yolk sac cells: viability and expression of cell markers during maternal diabetes

The function of the visceral yolk sac (VYS) is critical for embryo organogenesis until final fetal development in rats, and can be affected by conditions such as diabetes. In view of the importance of diabetes during pregnancy for maternal and neonatal health, the objective of this study was to assess fetal weight, VYS cell markers, and viability in female Wistar rats (200-250 g) with induced diabetes (alloxan, 37 mg/kg) on the 8th gestational day (gd 8). At gd 15, rats from control (n=5) and diabetic (n=5) groups were anesthetized and laparotomized to remove the uterine horns for weighing of fetuses and collecting the VYS. Flow cytometry was used for characterizing VYS cells, and for determining mitochondrial activity, cell proliferation, DNA ploidy, cell cycle phases, and caspase-3 activity. Fetal weight was reduced in the diabetic group. Expression of the cell markers CD34, VEGFR1, CD115, CD117, CD14, CCR2, CD90, CD44, STRO-1, OCT3/4, and Nanog was detected in VYS cells in both groups. In the diabetic group, significantly decreased expression of CD34 (P<0.05), CCR2 (P<0.001), and OCT3/4 (P<0.01), and significantly increased expression of CD90 (P<0.05), CD117 (P<0.01), and CD14 (P<0.05) were observed. VYS cells with inactive mitochondria, activated caspase-3, and low proliferation were present in the rats with diabetes. Severe hyperglycemia caused by maternal diabetes had negative effects on pregnancy, VYS cell viability, and the expression of cell markers.     

Cytomorphology of yolk sac tumor of the liver in fine-needle aspiration: a pediatric case

Yolk sac tumors (YST) in extragonadal locations are rare. Cytologic diagnosis of YST on fine-needle aspiration (FNA) smears may be a challenge to the cytopathologist. Further neo-adjuvant therapy may be based on cytologic diagnosis making accuracy important. We studied FNA material from a hepatic mass in a pediatric patient to further define the cytomorphologic features of hepatic YST. Features include large pleomorphic balls of tumor cells with high nuclear to cytoplasmic ratios, papillary or microglandular pattern of growth, cytoplasmic and intranuclear vacuoles, and prominent nucleoli. Positive immunohistochemical studies included alpha-fetoprotein, cytokeratin AE1/AE3, and CAM 5.2, which are useful in supporting the diagnosis. We report a pediatric patient in whom the diagnosis of hepatic YST was made by cytologic, histologic, and immunohistochemical studies. The subsequent liver biopsy was consistent with the FNA diagnosis. Our findings may further help to characterize the cytomorphologic features of this rare lesion.     

Hepatoid variant of yolk sac tumor of the testis

A case of testicular yolk sac tumor (endodermal sinus tumor) consisting predominantly of hepatoid cells is documented. A mass measuring approximately 4 x 3 cm was noted in the left testis of a 64-year-old man. Preoperative examination revealed an elevated serum level of alpha-fetoprotein (5479 ng/mL). Histologically, the lesion was composed predominantly of sheet-like or trabecular proliferation of hepatocyte-like cells with eosinophilic or clear cytoplasm. The tumor cells were immunoreactive for alpha-fetoprotein, antimitochondrial antibody, cytokeratin (AE1/AE3), alpha-1-antichymotrypsin, alpha-1-antitrypsin, albumin, carcinoembryonic antigen and epithelial membrane antigen. It was necessary to distinguish this variant lesion from metastatic hepatocellular carcinoma, embryonal carcinoma and hepatoid carcinoma.     

Identification of erythroid-enriched gene expression in the mouse embryonic yolk sac using microdissected cells.

Little is known about the genes that control the embryonic erythroid program. Laser capture microdissection was used to isolate primitive erythroid precursors and epithelial cells from frozen sections of the embryonic day 9.5 yolk sac. The RNA samples were amplified and labeled for hybridization to Affymetrix GeneChip Mouse Genome 430A 2.0 arrays. Ninety-one genes are expressed significantly higher in erythroid than in epithelial cells. Ingenuity pathway analysis indicates that many of these erythroid-enriched genes cluster in highly significant biological networks. One of these networks contains RBTN2/LMO2, SCL/TAL1, and EKLF/KLF1, three of the very few genes required for primitive erythropoiesis. Quantitative real-time polymerase chain reaction was used to verify that platelet factor 4, reelin, thrombospondin-1, and muscleblind-like 1 mRNA is erythroid-enriched. These genes have established roles in development or differentiation in other systems, and are, therefore, good candidates for regulating primitive erythropoiesis. These results provide a catalog of genes expressed during primitive erythropoiesis.     

Ultrastructural changes of the early visceral yolk sac layer of mouse embryos after maternal injection of trypan blue

Summary The ultrastructural features of the early visceral yolk sac epithelium of normal mouse embryos on day 9 were compared to those whose mothers had received a single subcutaneous injection of 100 mg/kg trypan blue on day 8. The following results were obtained: In normal embryos the visceral yolk sac cells are predominantly characterized by numerous membrane bounded inclusions localized in the supranuclear cytoplasm. In embryos of animals treated with trypan blue, at about 12h after injection large single and only partly membrane bounded vacuoles are observed occupying most of the apical cytoplasm. Up to 24h after injection large cytoplasmic areas are seen which are in a stage of autodigestion possibly due to leakage of the vacuolar content. These alterations are exclusively limited to the visceral yolk sac epithelium whereas in the cells of the embryonic part, e.g. head process, no changes could be found. The observations are discussed in relation to the mechanism of the teratogenic activity of trypan blue.This investigation has kindly been supported by a grant of the Deutsche Forschungsgemeinschaft (Schl 166/1)     

Predictive value of human chorionic gonadotrophin in the outcome of early pregnancy after in-vitro fertilization and spontaneous conception

This prospective study analyses the value of the -subunit ofhuman chorionic gonadotrophin (-HCG) in 120 pregnancies obtainedafter in-vitro fertilization (IVF)-embryo transfer. Spontaneousconception cycles (n = 16) were also analysed allowing a comparisonbetween these two forms of conception. Of the 120 clinical pregnancies,48 started as single gestations and 50 started with two or moresacs. There were 14 clinical abortions and eight ectopic pregnancies.All subjects had blood samples taken under a fixed protocolon days 11, 14, 17, 20 and 23 after follicular aspiration. Weeklysamples were obtained thereafter until day 60 from ovum retrieval.Transvaginal ultrasounds were performed at weekly intervals,starting on day 23 after follicular aspiration. In spontaneousconception cycles blood samples were obtained daily, startingon the day of follicular rupture. In spontaneous conceptioncycles and in IVF– embryo transfer conceptions, the doublingtime (DT) of ;-HCG was 1.4 ± 0.3 and 1.6 ± 0.4days respectively. This difference was not significant. In multigesta–tions,the DT was 1.5 ± 0.3 days. The absolute values of -HCGin early spontaneous gestations were significantly higher thanin IVF—embryo transfer cycles, suggesting that the blastocystimplants with less cellular mass when initiated in vitro ascompared with the in-vivo condition. The early prediction ofectopic pregnancy and spontaneous clinical abortion was analysedby the -HCG profile as well as the absolute values in comparisonto normal pregnancies. Both parameters showed significant differencesas early as the interval between days 11 and 23 from follicularaspiration. This study provides a comprehensive approach tothe evaluation of the outcome of early gestation in terms ofthe predictability of single and multigestation, ectopic pregnancyand early abortion.     

Yolk sac endoderm is the major source of serum proteins and lipids and is involved in the regulation of vascular integrity in early chick development

An important function of the vascular system is nutrient delivery. In adult animals, this is mediated through a close contact of the mesoderm‐derived vasculature with the endoderm‐derived enterocytes and hepatocytes. During embryonic development, the yolk sac (YS) endoderm has been suggested to play a similar role. Physiological and molecular nature of the contact between the YS endoderm and the vasculature is not well‐understood. To understand roles of the YS endoderm in early development, we used the avian model and carried out a gene expression profiling analysis of isolated area vasculosa YS endoderm tissues from embryonic day 2–4 chick embryos, covering the first 48 hr of postcirculation development. Genes involved in lipid metabolism are highly enriched, indicating an active modification of lipid components during their transfer from the yolk to the circulatory system. We also uncovered genes encoding major serum proteins and key regulators of vascular integrity. In particular, PTGDS, an enzyme controlling the last step of prostaglandin D2 production, shows high expression in the YS endoderm. Experimental introduction of prostaglandin D2 into embryonic circulation led to intraembryonic vessel rupture. These data suggest that the YS endoderm is the major, if not exclusive, source of lipid and protein constituents of the early embryonic serum and plays an important role in the regulation of vascular integrity in developing embryo. Developmental Dynamics 240:2002–2010, 2011. © 2011 Wiley‐Liss, Inc.     

人卵黄囊间质干细胞的分离纯化及诱导成脂的实验研究

目的:分离纯化及体外定向诱导人卵黄囊间质干细胞(YS-MSC)分化为脂肪细胞。方法:显微分离人卵黄囊, 经酶消化得到卵黄囊细胞, 卵黄囊细胞经贴壁培养、传代纯化得到人YS-MSC, 流式细胞仪检测YS-MSC表面抗原表达, 钙钴法测定碱性磷酸酶(AKP)活性;地塞米松、消炎痛、胰岛素定向诱导YS-MSC分化为脂肪细胞。油红O检测中性脂肪。结果:人卵黄囊间质干细胞易于分离、纯化, 体外培养增殖潜能大。卵黄囊间质干细胞CD29、CD44、CD166及CD105表达阳性, CD34、CD45和CD86为阴性;AKP弱阳性。卵黄囊间质干细胞经成脂诱导转化为大小不等的园形或椭圆形细胞, 可见胞浆内有少量微小脂滴形成, 随时间延长, 胞浆中脂滴相互融合, 胞核被挤于细胞的一侧, 经油红O染色脂滴染橘红色, 符合脂肪细胞的生物学特征。结论:人卵黄囊间质干细胞与成体间质干细胞表型一致, 在体外可以分化为脂肪细胞。