**Question:** Which are seen in endodermal sinus tumor

**Core Concept:** Endodermal sinus tumor (ETS) is a rare and aggressive germ cell tumor typically found in children and adolescents. It is a type of embryonal carcinoma and is associated with poor prognosis.

**Why the Correct Answer is Right:** Endodermal sinus tumor is characterized by the presence of endodermal sinus cells, which are derived from the endoderm layer of the embryonic yolk sac. These cells exhibit differentiated endodermal features, such as the production of glycogen and mucin.

**Why Each Wrong Option is Incorrect:**

A. **Option A:** Oligodendroglioma - This refers to a type of brain tumor originating from glial cells. It is distinct from endodermal sinus tumor.

B. **Option B:** Astrocytoma - Similar to oligodendroglioma, this refers to a glioma arising from astrocytes. It is distinct from endodermal sinus tumor.

C. **Option C:** Ependymoma - This represents a type of brain tumor originating from ependymal cells lining the central nervous system (CNS) and is distinct from endodermal sinus tumor.

D. **Option D:** Medulloblastoma - This is a type of pediatric brain tumor originating from neural stem cells in the cerebellum, distinct from endodermal sinus tumor.

**Clinical Pearl / High-Yield Fact:**

In the differential diagnosis of a suspected germ cell tumor, endodermal sinus tumor should be considered in patients with a history of exposure to diethylstilbestrol (DES) during pregnancy, as DES is a known teratogenic agent associated with an increased risk of ETS.

**Correct Answer:** D. Medulloblastoma

ETS is a distinct entity while medulloblastoma is a separate type of pediatric brain tumor. Both are important to know for differential diagnosis in cases of suspected germ cell tumors, particularly in the context of DES exposure during pregnancy, which increases the risk of ETS.