The
histology of EST is variable, but usually includes malignant endodermal cells. These cells secrete
alpha-fetoprotein (AFP), which can be detected in tumor tissue,
serum,
cerebrospinal fluid,
urine and, in the rare case of fetal EST, in
amniotic fluid. When there is incongruence between
biopsy and AFP test results for EST, the result indicating presence of EST dictates treatment. This is because EST often occurs as small "malignant foci" within a larger tumor, usually
teratoma, and biopsy is a sampling method; biopsy of the tumor may reveal only teratoma, whereas elevated AFP reveals that EST is also present. GATA-4, a
transcription factor, also may be useful in the diagnosis of EST. Diagnosis of EST in
pregnant women and in
infants is complicated by the extremely high levels of AFP in those two groups. Tumor surveillance by monitoring AFP requires accurate correction for gestational age in pregnant women, and age in infants. In pregnant women, this can be achieved simply by testing
maternal serum AFP rather than
tumor marker AFP. In infants, the tumor marker test is used, but must be interpreted using a reference table or graph of normal AFP in infants.
Pathology EST can have a multitude of morphologic patterns including: reticular, endodermal sinus-like, microcystic, papillary, solid, glandular, alveolar, polyvesicular vitelline, enteric and hepatoid. File:Histopathology of endodermal sinus tumor with Schiller–Duval bodies.png|Histopathology of endodermal sinus tumor with Schiller–Duval bodies.(a) papillary pattern combined with small tubopapillary endodermal sinus structure (Schiller–Duval body) in blue circle;(b) marked tubulopapillary sinusoidal structure with central vascular core in longitudinal section (Schiller–Duval body);(c,d) 400× g magnified image plus zoom of diagnostic round cystic Schiller–Duval body in a transverse section, with microcystic and papillary patterns around. The body has a central vessel surrounded by fibrous tissue, called the fibrovascular core, and it is surrounded by layers of the tumoral cells at the surface of that stalk. The structure is located in open cystic space also lined by tumoral cells. All those structures together are called a Schiller–Duval body and resemble primitive glomerulus. H&E stain.
Schiller–Duval bodies on
histology are
pathognomonic and seen in the context of the endodermal sinus-like pattern. Rarely, it can be found in the vagina. ==Treatment==