Renal Yolk Sac Tumor Clinically Misdiagnosed as Nephroblastoma: A Case Report.

Background: Yolk sac tumor is a germ cell tumor (GCT) that occurs in infants and adolescents and affects various sites. There is a trend to treat pediatric renal tumors before a tissue diagnosis. We report a renal yolk sac tumor clinically misdiagnosed as Wilms tumor, based on ultrasound (US) and MRI.Case Report: This 21-month-old male infant was discovered to have a space occupying lesion in the right kidney. Because the tumor was large, initial radiotherapy preceded surgical resection. Histologically, the tumor was a yolk sac tumor.Conclusion: Imaging examination of renal yolk sac tumor can easily be misdiagnosed as Wilms tumor. SIOP treatment plan for Wilms tumor requires preoperative chemotherapy, which is different from the treatment regimen for yolk sac tumor. Preoperative alpha-fetoprotein could have been helpful in avoiding this clinical misdiagnosis.

Primary vaginal endodermal sinus tumor in infants and children: experience from a tertiary center.

BACKGROUND: The objective of the study was to analyze the clinical features, treatment, and outcomes of primary vaginal endodermal sinus tumor (EST) in infants and children treated in a tertiary center. METHODS: Clinical data of patients with pathologically confirmed primary vaginal EST in our hospital from January 1997 to December 2017 were retrospectively reviewed and analyzed. RESULTS: A total of 21 patients were included in this study. The median age at diagnosis was 11 months (range, 4-44 months). The most common manifestations were abnormal vaginal bleeding, and a polypoid mass protruding from the vagina. Chemotherapy based on PEB (cisplatin, etoposide, bleomycin) regimen was given, and serum alpha-fetoprotein (AFP) levels dropped to normal levels after 2 to 4 cycles of chemotherapy (median, 2 cycles). After 3 to 13 cycles of chemotherapy, with a median of 5 cycles, 20 patients achieved complete remission (95.2%). The median follow-up time was 80 months (range, 4-281months). At the time of the last follow-up, 19 cases were alive without disease, and the survival rate was 90.5%. CONCLUSION: Vaginal EST is a very rare malignant germ cell tumor and is sensitive to chemotherapy. Conservative surgery combined with PEB chemotherapy is an effective way of treatment. Serum AFP and imaging examinations can monitor the treatment response and recurrence.

Yolk sac tumours of the orbit and sinonasal tract.

PURPOSE: The aim of this study is to report two cases of paediatric Yolk sac tumours (YST) of the orbit and sinonasal tract, with a major review on the subject. METHODS: Two case reports along with a comprehensive retrospective literature review of all English language publications between 1974 and 2021 is presented. Literature review examined the demographics, clinical presentation and diagnostic and prognostic factors of extragonadal YSTs of the orbit and sinonasal tract. RESULTS: Orbit and sinuses are rare sites for YST, with only 25 paediatric cases reported in the literature. Extragonadal yolk sac tumours carry a significantly worse outcome than those localised to the gonads, with the 5-year survival of 66% and 81-89%, respectively. Our review found the median age of presentation to be 18 months (18 months for males and 24 months for females), and females are more commonly affected. The most common presentations were proptosis, facial swelling and ophthalmoplegia. Treatments and therefore outcomes varied in the cases due to the large time period. Of the cases reported in the last 10 years, all patients with data provided were alive and disease-free at follow-up. CONCLUSION: Sino-orbital yolk sac tumours are rare and have variable presentations, dependent on the extent of local invasion. Early diagnosis and treatment with multimodal therapy are paramount in having improved overall survival.

Imaging Findings and Clinical Analysis of Primary Intracranial Pure Yolk Sac Tumors in Children and Adolescents: A Retrospective Study from China.

BACKGROUND AND PURPOSE: Primary intracranial pure yolk sac tumor is very rare. Our aim was to summarize the characteristics of primary intracranial pure yolk sac tumors from the clinical and imaging aspects in a retrospective study. MATERIALS AND METHODS: We studied 5 patients with primary intracranial pure yolk sac tumors in Guangzhou Women and Children's Medical Center from January 2015 to June 2021. A comprehensive literature search was performed on the electronic database of the China National Knowledge Infrastructure (1990 to June 2021). Clinical data based on age, sex, treatment, CT, and MR imaging findings were collected and analyzed. RESULTS: A total of 25 patients were included in the study, 21 boys and 4 girls. Twenty-one patients underwent plain MR imaging and an enhanced examination, 9 patients underwent DWI, and 12 patients underwent plain CT and/or an enhanced examination. The tumors were posterior fossa in 9 cases and supratentorial in 16 cases. All tumors showed marked enhancement after enhanced scanning by MR imaging or CT. The signal on DWI was similar to that of the cerebral cortex, and the ADC map was similar to or slightly higher than that of the cerebral cortex. Among the cases, 13 were followed up from 2 months to 5 years. There was no recurrence or metastasis in 9 patients with postoperative chemotherapy or chemoradiotherapy followed up for 1.5-5 years. Four patients died 2 months to 1.5 years after only an operation, or chemoradiotherapy but no operation. CONCLUSIONS: There are some relatively specific imaging findings of primary intracranial yolk sac tumors that could assist in their diagnosis. Surgery combined with radiation therapy and/or chemotherapy can achieve a better prognosis.

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

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

Sinonasal SMARCB1 (INI1) Deficient Carcinoma with Yolk Sac Tumor Differentiation: A Case Report and Treatment Options.

SMARCB1 (INI1) deficient carcinoma (SDC) is a newly-described, aggressive, high-grade malignancy of the adult population. Rarely, these tumors demonstrate yolk sac differentiation. Treatment protocols are not defined due to the rarity of this entity. A 55 year-old-male presented with a tumor originating in the maxillary sinus. He was treated with neoadjuvant therapy followed by radical surgery and adjuvant treatment. We review the literature and discuss the course of disease and treatments of sinonasal SDC with yolk sac tumor differentiation. To our knowledge, this is the sixth reported case of sinonasal SDC with yolk sac tumor differentiation. This is the first publication describing the clinical course and efficacy of therapeutic interventions.

Pregnancy and Delivery After Ovarian Yolk Sac Tumor: A Case Report.

BACKGROUND A yolk sac tumor (YST) is a rare, malignant tumor of cells that line the yolk sac of the embryo. It most frequently occurs in the ovary (ovarian yolk sac tumor: OYST) in children and adolescents. Thus, fertility-preservation treatment is a concern. CASE REPORT A 24-year-old nulliparous woman visited us for infertility treatment and then right OYST was detected. A unilateral right salpingo-oophorectomy, infra-colic omentectomy, ipsilateral lymph node dissection, and peritoneal biopsies were performed. Histological examination confirmed the diagnosis of a stage IC OYST. Six cycles of bleomycin-etoposide-cisplatin chemotherapy were performed. She had no recurrence over the next 16 months. She conceived by in-vitro fertilization, and abdominally gave birth to a term infant. Both mother and baby had a smooth recovery. CONCLUSIONS This case adds further evidence to the 5-year survival and progression-free survival following surgery and chemotherapy in OYSTs, while preserving fertility.

A primary mediastinal germ cell tumor of yolk sac type: case report.

The mediastinal malignant germ cells tumor represents less than 0.5% of thoracic tumors, although the mediastinum is one of the main extragonadic locations of these tumors. In the majority of cases, young people are those most affected. The prognosis of mediastinal malignant germ cells tumors is poor, especially non-seminomatous germ tumors. In this article, we report a rare case of a young 19-years-old patient treated for a mediastinal germ cell tumor of yolk sac. The patient presented a chest pain; the chest computed tomography (CT) showed a right paramedian mediastinal mass with a pleural effusion associated with supraclavicular and cervical lymph nodes. Biopsy revealed a non-seminomatousgerm cell tumor of yolk sac. The exams showed elevated alpha-fetoprotein (AFP), without any meaningful elevation of other serictumor markers. The patient received 4 cycles of chemotherapy based on etoposide, ifosfamide and platinum salts then a complete excision of the mass.

Multidisciplinary treatment of primary intracranial yolk sac tumor: A case report and literature review.

RATIONALE: Intracranial yolk sac tumors (YSTs) are rare malignancies with limited treatment options and a dismal prognosis. They are usually managed with surgical resection and chemoradiotherapy. PATIENT CONCERNS: Here, we report a patient with primary YST in the pineal region who achieved long term survival. Despite undergoing treatment, he experienced several recurrences over a 15-year period. DIAGNOSIS: Brain magnetic resonance imaging (MRI) demonstrated the presence of space-occupying lesions in the pineal region and the medial tail of the left lateral ventricle. The tumors were excised, and the histological diagnosis suggested an intracranial YST. INTERVENTIONS: The patient achieved long term survival after combined modality therapy including surgery, stereotactic radiosurgery (SRS)/intensity modulated radiation therapy (IMRT), chemotherapy, and targeted therapy. OUTCOMES: The disease remained stable. However, the patient gave up treatment and passed away in October 2020, with a total survival of about 15 years. LESSONS: To the best of our knowledge, this patient with intracranial YST had received a longer survival compared with other published reports. We summarize previously published reports of intracranial YST and discuss the importance of multidisciplinary treatment. SRS may have a role, as a focal boost to residual tumor after resection or in case of recurrence after conventional radiotherapy, in the multimodality management of intracranial YSTs.

Primary yolk sac tumor of pterygopalatine fossa with loss of vision: A case report.

INTRODUCTION: Primary yolk sac tumor (YST) is an infrequently-diagnosed malignant extragonadal germ cell tumors. It is likely to recur locally and may present with widespread metastases once diagnosed. Primary YST of the head is uncommon but can cause severe complications, such as loss of vision once the tumor mass invades the optic nerve. PATIENT CONCERNS: A 20-month-old boy presented to the general clinic of the local children's hospital with a complaint of swelling of left face for 1 year and proptosis of the left eye for over 2 weeks as stated by his parents. Initially, he did have some vision, as he could walk by himself, but a special ophthalmologic examination was not performed. DIAGNOSES: Cranial computed tomography and magnetic resonance imaging revealed a large tumor accompanied by peripheral bone destruction in the left pterygopalatine fossa that extended to sphenoid, ethmoid, left maxillary sinuses, left nasoethmoid, and left orbit. The optic nerve was invaded on both sides. Chest and abdominal imaging were normal. A primary diagnosis of Langerhans cell hyperplasia was made. However, blood tests on the second day of hospitalization revealed significantly elevated serum alpha-fetoprotein levels. On the third day, the boy lost his eyesight, with loss of pupillary and no light sensation during flashlight stimulation on both sides. INTERVENTIONS: Nasal endoscopy was performed on the fourth day, the vast majority of soft tissue mass was resected for biopsy. Histopathological examination revealed features of endodermal sinus tumor. A final diagnosis of primary YST of pterygopalatine fossa was made. Because the mass could not be resected completely, he received combined chemotherapy with bleomycin, etoposide, and carboplatin for 6 cycles over six months. OUTCOMES: The patient recovered with significant tumor shrinkage and without secondary metastasis after 18 months but left permanently blind. CONCLUSION: The worst complication of loss of vision after Primary YST of pterygopalatine fossa alerts us that close physical examination during the initial investigation should be performed, which is especially important in young children who cannot express complaints well. Early detection and treatment with surgical resection and chemotherapy may contribute to satisfactory outcomes and avoidance of visual impairment.

Multimodal Treatment of Children With Sacrococcygeal Yolk Sac Tumor: Retrospective Analysis of Clinicopathology Characteristics and Relapse-free Survival.

The aim of the study was to explore the clinicopathologic characteristics of sacrococcygeal yolk sac tumor (SYST) associated with relapse and the role of sensitivity to neoadjuvant chemotherapy in predicting outcome. The authors investigated prognostic factors of age, stage, initial tumor size, pathologic response to neoadjuvant chemotherapy, and alfa fetoprotein. A total of 26 patients with SYST were enrolled. Neoadjuvant chemotherapy was administered to 20 cases. Six patients underwent resection as initial therapy. Recurrence occurred in 12 patients. Nine patients with specimens exhibiting no malignant component after chemotherapy did not experience recurrence. By contrast, relapses occurred in 7 of 11 patients with viable residual tumor after neoadjuvant chemotherapy. All relapsed patients still achieved partial remission or complete remission after salvage therapy. Five-year relapse-free survival and overall survival rates were 55.2% and 100%, respectively (median follow-up, 59.5 mo; range, 16 to 155). Patients with complete necrosis after neoadjuvant chemotherapy had a better outcome compared with children with viable residual tumor. Relapse-free survival of pediatric SYSTs in this cohort were still low and warrants the multidisciplinary effort.

Somatically Derived Yolk Sac Tumor of the Ovary in a Young Woman.

Ovarian carcinoma with a somatically derived yolk sac tumor component is a phenomenon known to mostly occur in postmenopausal women. Herein, we report an ovarian endometriosis-associated somatic yolk sac tumor arising in the background of a low-grade endometrioid adenocarcinoma in a young woman. A 27-yr-old woman presented with abdominal pain, subsequently recognized to be caused by a right ovarian mass undergoing torsion. Following operative management, microscopic examination of the salpingo-oophorectomy specimen showed endometriosis and a predominantly cystic ovarian neoplasm with 2 distinct phenotypic areas: (1) a yolk sac tumor component containing Schiller-Duval bodies and (2) a low-grade endometrioid carcinoma component with squamous metaplasia. Immunohistochemical evaluation showed distinct profiles in the yolk sac tumor (estrogen receptor/progesterone receptor/PAX8 negative, SALL4/Glypican 3 positive) and endometrioid (estrogen receptor/progesterone receptor/PAX8 positive, SALL4/Glypican 3 negative) components. Given these findings, the diagnosis of an endometriosis-associated endometrioid adenocarcinoma with a somatically derived yolk sac tumor was rendered. The tumor was staged as pT1c1 due to intraoperative spillage. The patient underwent chemotherapeutic treatment and after 15 mo of follow-up, she was alive with no evidence of recurrence. This example demonstrates that somatic yolk sac tumor differentiation in ovarian epithelial neoplasia can occur in young patients; awareness of this phenomenon is important as somatic and germ cell yolk sac neoplasia have different behavior and therapy.

To Transplant or Not to Transplant During the SARS-CoV-2 Pandemic? That Is the Question.

The novel coronavirus disease 2019 has grown to be a global public health emergency. The rapid spread of the infection has raised many questions in the oncohematological scientific community regarding the appropriateness of high-dose chemotherapy with autologous stem cell transplantation (ASCT). We here report two cases of patients who received ASCT at our Institute during the epidemic in Italy, affected with Hodgkin lymphoma and germ cell tumor, respectively. The two patients underwent a nasopharyngeal swab for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on hospital admittance and during the period of bone marrow aplasia. They were attended to exclusively by dedicated health care staff who followed specifically implemented protocols for bedside nursing and care. They completed the procedure without unexpected side effect. Our experience demonstrates how ASCT can be performed safely if procedures are reorganized ad hoc to reduce the risk of SARS-CoV-2 infection.

Systemic treatment options for growing teratoma syndrome: A single-center experience with a comprehensive review of the literature.

BACKGROUND: Growing teratoma syndrome (GTS) is a very uncommon phenomena. Given its lower prevalence, there is little data about clinichopathological features and management of GTS. Literature about disease mostly composed of case reports. In this study, we aimed to report patients characteristics and treatment modalities in our center within a relatively large cohort. PATIENTS AND METHODS: We retrospectively reviewed the clinical records 21 patients who fulfilled criteria of GTS. Survival analysis was performed by using the Kaplan-Meier method with the Long-rank test. p<0.05 was considered statistically significant. RESULTS: The median age at diagnosis was 25 (range 17-51). A total of 12 patients could have undergone surgery. Of patients who underwent surgery, 5 patients remained fully disease free, and 7 patients had experienced disease recurrences. Nine patients had unresectable disease, and treated with either platin-based chemotherapy or interferone α2b. Of those, 5 patients eventually had undergone autologous stem cell transplantation (ASCT) with surprisingly promising response rates. One patient had complete response and three patients had partial response. One patient died soon after ASCT due to infectious complication. CONCLUSION: GTS is an unique entity with regard to its clinicopathological features and available treatment options as we mentioned in the text. Despite various agents reported to have efficacy in case reports, surgery remains as the mainstay of treatment. According to result of our study, ASCT and platin-based chemotherapy regimens may be feasible options for patients with unresectable disease.

Vasculogenic Mesenchymal Tumor: A Clinicopathologic and Molecular Study of 55 Cases of a Distinctive Neoplasm Originating From Mediastinal Yolk Sac Tumor and an Occasional Precursor to Angiosarcoma.

We report 55 postchemotherapy resections of primary nonseminomatous mediastinal germ cell tumors with prominent vasculogenic features showing the formation of rudimentary to well-developed neoplastic vessels within primitive mesenchyme. These cases represented 25% of a cohort of 221 such specimens. The patients were 19 to 49 years old (mean, 28 y) and 98% had serological evidence of yolk sac tumor. The vasculogenic lesions, felt to represent a neoplastic reiteration of embryonic vasculogenesis in the splanchnic mesoderm of the yolk sac, were further subdivided into teratoma with vasculogenic stroma (n=9), vasculogenic mesenchymal tumor (VMT) (n=42, further classified into low grade [n=24] and high grade [n=18]), and angiosarcoma (n=4). The distinction of teratoma with vasculogenic stroma from VMT was based solely on the greater extent of VMT (exceeding 1 low power [×4 objective] microscopic field), with both categories showing a spectrum of vessels lined by atypical endothelium in a nonendothelial neoplastic stroma that often also generated vascular walls comprised of atypical smooth muscle. The angiosarcomas showed stratification of highly atypical endothelial cells or anastomosing vessels lined by nonstratified but cytologically similar endothelium. Immunohistochemical studies supported the generation of neoplastic vessels from the tumor stroma, most commonly by the development of stromal clefts showing reactivity for podoplanin, CD34, and occasionally ERG, followed by the gradual development from the clefts of thin-walled vessels that later became encircled by stromal cells showing smooth muscle differentiation by immunohistochemistry. Occasionally, round collections of stromal erythrocytes became surrounded by stromal cells to generate blood vessels. Fluorescence in situ hybridization showed chromosome 12p copy number increase in both the endothelial component and stromal component in 8/9 VMT cases and in 1/1 angiosarcoma. On follow-up, no patient with teratoma with vasculogenic stroma had evidence of a subsequent vascular tumor or sarcoma, whereas 8 of the 35 (23%) patients with VMTs (2 low grade and 6 high grade) and meaningful follow-up developed sarcoma (1 angiosarcoma, 2 rhabdomyosarcomas, and 5 not further characterized). The difference between low-grade and high-grade tumors was of borderline significance (P=0.058). Two of the 4 patients with angiosarcoma died of metastatic angiosarcoma, with the other 2 disease-free at 6.8 and 7 years. Compared with the 165 patients with follow-up and no vasculogenic lesions, there was a highly significant (P=4.3×10-5) association of any vasculogenic lesion with sarcomatoid tumors during the clinical course of VMT patients. In addition, 5/46 patients with follow-up and vasculogenic lesions (11%) died of either leukemia or myelodysplastic syndrome compared with 2 of 166 (1%) lacking them (P=0.0012). Three of the 5 patients had identifiable immature hematopoietic cells within their vasculogenic lesions, but 4 other VMT patients with these did not develop leukemia or myelodysplasia. We conclude: (1) vasculogenic lesions are frequent in postchemotherapy resections of primary mediastinal germ cell tumors with yolk sac tumor components; (2) they mostly consist of neoplastic vessels in a stroma that also generates neoplastic vascular walls of smooth muscle; (3) VMTs are associated with an increased incidence of sarcomas, even though most vasculogenic lesions in this context do not meet criteria for angiosarcoma; (4) the presence of vasculogenic lesions in postchemotherapy resections of primary mediastinal germ cell tumors place patients at increased risk for leukemia or myelodysplasia.

Need for risk-adapted therapy for malignant ovarian germ cell tumors: A large multicenter analysis of germ cell tumors' patients from French TMRG network.

BACKGROUND: Malignant ovarian germ cell tumors are rare tumors, affecting young women with a generally favorable prognosis. The French reference network for Rare Malignant Gynecological Tumors (TMRG) aims to improve their management. The purpose of this study is to report clinicopathological features and long-term outcomes, to explore prognostic parameters and to help in considering adjuvant strategy for stage I patients. PATIENTS AND METHODS: Data from patients with MOGCT registered among 13 of the largest centers of the TMRG network were analyzed. We report clinicopathological features, estimated 5-year event-free survival (5y-EFS) and 5-year overall survival (5y-OS) of MOGCT patients. RESULTS: We collected data from 147 patients including 101 (68.7%) FIGO stage I patients. Histology identifies 40 dysgerminomas, 52 immature teratomas, 32 yolk sac tumors, 2 choriocarcinomas and 21 mixed tumors. Surgery was performed in 140 (95.2%) patients and 106 (72.1%) received first line chemotherapy. Twenty-two stage I patients did not receive chemotherapy. Relapse occurred in 24 patients: 13 were exclusively treated with upfront surgery and 11 received surgery and chemotherapy. 5y-EFS was 82% and 5y-OS was 92.4%. Stage I patients who underwent surgery alone had an estimated 5y-EFS of 54.6% and patients receiving adjuvant chemotherapy 94.4% (P < .001). However, no impact on estimated 5y-OS was observed: 96.3% versus 97.8% respectively (P = .62). FIGO stage, complete primary surgery and post-operative alpha fetoprotein level significantly correlated with survival. CONCLUSION: Adjuvant chemotherapy does not seem to improve survival in stage I patients. Active surveillance can be proposed for selected patients with a complete surgical staging.

Establishment and Characterization of a Novel Primitive Yolk Sac Tumour Cell Line, TC587.

BACKGROUND/AIM: Yolk sac tumour (YST) is a rare malignant ovarian germ cell tumour that often occurs in young women or adolescents and exhibits an unfavourable outcome. To evaluate the biological behavior of carcinomas in vitro, permanent tumour cell lines are required. However, previously, only a few human YST cell lines have been established. Therefore, we aimed to establish a novel YST cell line. MATERIALS AND METHODS: We established a novel YST cell line, TC587, from an adolescent patient with ovarian YST. RESULTS: The cell line expressed AFP and SALL4, the characteristics of YST. In addition, we evaluated somatic mutations using next-generation sequencing and revealed some pathogenic variants, including mutations in the NRAS, KIT, KMT2C, RSF1, and TP53 genes. CONCLUSION: The newly established TC587 cell line may represent an effective tool for developing treatments and conducting molecular analyses for YST.

Yolk sac tumor of vagina: a rare cause of vaginal bleeding in adolescents - a case report.

Yolk sac tumor (YST) is one of the malignant germ-cell tumors (MGCT) that usually occurs in the ovaries and testes of young patients. Its occurrence in the vagina is extremely rare. We present a rare case of extragonadal YST occurring in the vaginal region. A 12-year-old girl, presented with vaginal bleeding and pain in the perineal region. Physical exam identified a limited pelvic mass, 5 x 4cm in size. Abdominal ultrasound and magnetic resonance imaging (MRI) showed a heterogeneous mass in cervico-vaginal region. The patient was taken to the surgery, where an excisional biopsy was obtained. The diagnosis of YST is confirmed by histopathology and immunohistochemistry studies. However, the tumor marker (alpha fetoprotein and BHCG) was normal. The patient was treated according to the French TGM-95 protocol. Surgery was done after chemotherapy, hysterectomy in front of the cervical invasion, with a good decline at 2 years of end of treatment.

Extragonadal Yolk Sac Tumor Limited to the Myometrium: Report of a Case With Potential Fertility Preservation and Molecular Analysis Suggesting Germ Cell Origin.

Extragonadal pelvic yolk sac tumor (YST) in postpubertal female patients is a rare malignant neoplasm with potentially 2 distinct histogenetic pathways, and no clear treatment algorithm, especially in young patients desiring future fertility. Here we report a case of extragonadal YST arising within the myometrium in a 30-yr-old nulligravid woman. The patient presented with heavy and irregular bleeding, and imaging studies showed an 8.2 cm uterine mass, most consistent with a degenerating uterine leiomyoma. The patient underwent abdominal myomectomy, and intraoperative frozen section evaluation revealed a high-grade malignancy. Because of the patient's strong desire for future fertility, a conservative wedge resection of the surrounding myometrium and surgical staging with uterine closure and retention of the ovaries were performed. On permanent sections the tumor showed an admixture of glandular, reticular, solid and papillary architectural patterns, moderate to marked nuclear atypia and clear cytoplasm with focal eosinophilic hyaline globules. Immunohistochemical stains were diffusely positive for SALL4, AFP, glypican3, and focally positive for CK20, and negative for EMA, and CK7, confirming the diagnosis of extragonadal YST. The endometrium displayed normal secretory phase morphology without involvement by YST, and the myometrial resection margins were negative. Short tandem repeat genotyping analysis of the tumor revealed allelic gains at 7 loci (involving chromosomes 2, 3, 4, 5, 8, 13, and 15) and allelic loss at one locus assessed on chromosome 11, while next-generation sequencing results showed no mutations in 155 genes tested, suggesting germ cell origin. The patient underwent 4 cycles of adjuvant chemotherapy with bleomycin, etoposide, and cisplatin, and she had 1 cycle of successful oocyte cryopreservation 6 months after completing chemotherapy. The clinical follow-up at 12 mo shows no evidence of disease.