A Rare Case of Primary Mediastinal Endodermal Sinus Tumor Presenting with Hemoptysis

Mediastinal non-seminomatous germ cell tumors (NSGCTs) are very rare, with an approximate annual incidence of 500 in the United States. Here, we present a case of a 22-year-old male presenting with hemoptysis who was found to have primary mediastinal NSGCT, endodermal sinus tumor type (or yolk sac type). We review the imaging findings, pathology, and treatment of primary mediastinal endodermal sinus tumors.


Introduction
Extragonadal germ cell tumors (EGCTs) are uncommon pathologies, usually occurring in early childhood or early adulthood, with a male sex predilection [1]. They are characterized as either seminomatous or non-seminomatous types. These rare tumors have a poor prognosis, the worst of which occurs in the yolk sac and combined histopathologic tumors. Staging and thus prognosis of EGCT is based on both histopathology and imaging findings (i.e. bulky disease and distant metastatic disease) and thus, a multidisciplinary approach is best suited for the understanding and treatment of the disease [2].

Case Presentation
A 22-year-old incarcerated male with no known past medical history presented with a twomonth history of hemoptysis, subjective fevers, pleuritic chest pain, and unintentional weight loss of approximately 30 pounds. He had recently emigrated from El Salvador and was incarcerated for approximately seven months prior to symptom onset.
CT-angiography of the chest in the ED revealed a 12 cm mass in the anterior mediastinum, with mass effect on the superior vena cava (SVC), leftward displacement of the mediastinum and heart, and a right pleural effusion ( Figure 1). Notable labs included normocytic anemia, leukocytosis, and an elevated alpha-fetoprotein (AFP) with a normal β-hCG. Pathology was consistent with a non-seminomatous germ cell tumor of the yolk sac type (Figure 2). A followup testicular ultrasound showed no focal abnormalities ( Figure 3). 1 1 2   The patient was treated with one cycle of bleomycin, ifosfamide, cisplatin (BIP) and filgrastim chemotherapy before discharge. No additional outpatient information was available for internal assessment of the patient's status.

Discussion
Our patient was found to have a yolk sac tumor in the mediastinum. Mediastinal nonseminomatous germ cell tumors (NSGCTs) have an estimated annual incidence of approximately 500 in the United States. Mediastinal NSGCT commonly presents with nonspecific systemic signs, such as fever, weight loss, chest pain, cough, and hemoptysis [1]. Furthermore, presentation with Klinefelter syndrome and exogenous insulin production have also been reported [2].
EGCTs are rare and represent approximately 1-5% of all germ cell tumors [1,3]. Malignant EGCTs are grouped as either malignant seminomatous tumors (40%) or malignant nonseminomatous tumors (60%) [3]. ECGTs most commonly occur in the midline of the body and is thought to develop due to the failed migration of primary germ cells during embryogenesis, specifically, with 5-10% of all cases arising in the anterior mediastinum [4,5]. In the nonseminomatous category, yolk sac tumors have the worst prognosis. Yolk sac tumors (also known as endodermal sinus tumors) are most commonly seen as primary testicular tumors in infants and children under the age of three [2]. Whether gonadal or extragonadal, they release AFP tumor markers, and microscopic features are unequivocal, including reticular or microcystic proliferation and the characteristic Schiller-Duval bodies (which resemble primitive glomeruli) [2,5].
The treatment of extragonadal yolk sac tumours follows that of primary gonadal foci due to histologic similarities. Chemotherapeutic regimens usually include cisplatin, etoposide, and bleomycin. While surgical excision was previously not considered due to the assumption of metastasis, however, most recent studies suggest excisional surgery following successful treatment response to cisplatin-based chemotherapy [4,6]. Prognosis of germ cell tumors is based upon AFP levels, location, metastatic diseases, and the ability to have complete surgical resection [6]. Patients with a primary mediastinal focus are deemed to have a poor prognosis just based on location alone, giving them a five-year survival rate of 40-50% and a six-month survival rate following relapse [3,7].

Conclusions
This case outlined the presentation of an unfortunate 22-year-old male who presented with hemoptysis and was found to have a large anterior mediastinal mass. Although imaging provided detailed information about the characteristics of the mass, the differential remained broad. Eventually, the mass was biopsy-proven non-seminomatous germ cell tumor, yolk sac type. Due to the absence of any additional focus of tumor and a negative testicular ultrasound, his diagnosis was deemed to be a primary mediastinal yolk sac tumor (endodermal sinus tumor). The patient was treated with a cisplatin-based chemotherapeutic regimen.
Upon examining the literature, we have found that patients usually present with nonspecific systemic signs of malignancy, chest pain, cough, and hemoptysis. Treatment usually consists of a cistplatin-based chemotherapeutic regimen followed by surgical intervention. Unfortunately, yolk sac tumors have the worst prognosis of all extra-gonadal germ cell tumors with a prognosis of less than 50% at five years.

Additional Information Disclosures
Human subjects: Consent was obtained by all participants in this study.

Conflicts of interest:
In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: All authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work.