15 year-old male.
Admitted for cough and dyspnea
Hypermetabolic heterogeneous 12.3 cm AP x 11.6 cm LL x 11.8 cm CC mediastinal mass
- Lymphoma ( for example T-cell)
- Metastatic adenocarcinoma
- Yolk sac tumor
- Embryonal carcinoma
Yolk Sac Tumor
Yolk sac tumor or endodermal sinus tumor (EST) is a rare malignant germ cell tumor. Eighty percent occurs in the gonads. Mediastinal presentation is rare. When not arising from the gonads, EST is found on the midline and can affect the pineal gland, the mediastinum, the retroperitoneum and the coccyx.
Blood work demonstrate increased serum alpha-fetoprotein (AFP) and negative beta chorionic human gonadotrophin ( Beta hCG). Immunohistochemistry is positive for AFP, cytokeratine, SALL4 but negative for beta HCG, desmine.
This pathology is mostly found in young adults, not only in males but also in females. Clinical findings are related to the compressive effects of the mass in the thorax. While survival of the testicular form of the disease is around 75%, the survival for the mediastinal subtype is 25%.
Neoplasms arising from primordial germ cells includes germ-cell type neoplasms (embryonal carcinoma, seminoma, dysgerminoma), embryonic-type tumors (immature or mature teratomas) and extra-embryonic-type neoplams. The latter includes choriocarcinoma arising from the trophoblast and yolk sac tumor arising from the endoderm.
Cases reported in the literature include three occurrences of EST of the ovaries, one in the omentum and a few cases of mediastinal involvement. In all, F18-FDG uptake was high and in some F18-FDG PET-CT detected lesions not visualized by other modalities in patients with rising serum markers.
Final diagnosis: Yolk sac tumor
Terrible T's differential diagnosis
- Endodermal sinus tumor of the mediastinum. LD Truong et al. Cancer 1986;58:730-739
- High-level expression of divergent endodermal lineage markers in gonadal and extra-gonadal yolk sac tumors. H Shojaei et al. Modern Pathol 2016;29:1278-1288.
- Occult Mediastinal Yolk Sac Tumor producing AFP detected by F18-FDG PET/CT. M Liu et al . Clin Nucl Med 2016;41:585-586
- Integrated F18-FDG PET CT in endodermal sinus tumor. C Klieger et al. Int J Gynecol Cancer 2006;16:1685-1697
- Advance extragonadal yolk sac tumor serially followed up with F18 FDG PET CT and serum alpha-fetoprotein. T Baba et al. J Obstet Gyneacol Res 2012;38:605-609
- Detection of a metastatic lesion and tiny yolk sac tumors in two teenage patients by FDG-PET: report of two cases. M Takahashi et al. Surg Today 2014;44:1962-1965