FMGE 2019 — Pathology

Q: Which tumor arises from embryonic neural cells?

Medulloblastoma. ***Medulloblastoma*** - This tumor arises from **embryonic neural cells** in the **cerebellum**. - It is a highly malignant **brain tumor** most commonly found in children [1]. *Fibrous astrocytoma* - This is a type of **glioma** that arises from **mature astrocytes**, not embryonic neural cells. - It typically occurs in adults and can be found in various locations within the brain. *Neuroglioma* - This is a broad term that refers to **tumors of neuroglial origin**, meaning they arise from glial cells. - It does not specifically refer to a tumor originating from embryonic neural cells. *Ependymoma* - This tumor arises from **ependymal cells**, which line the **ventricles** and **spinal canal**. - While these are technically neural cells, they are more differentiated than the embryonic neural cells that give rise to medulloblastoma. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1314-1315.

Q: Acute graft rejection occurs within?

< 6 months. ***< 6 months*** - **Acute graft rejection** typically occurs within the first few **weeks to months** after transplantation due to a T-cell mediated immune response against the donor organ [1]. - While it can manifest at any time, the majority of cases occur within the **first 6 months** post-transplant, making this the most appropriate time frame [1]. *Few minutes* - Rejection presenting within minutes of transplantation is characteristic of **hyperacute rejection**, which is caused by pre-existing **donor-specific antibodies** [1]. - This rapid form of rejection is mediated by **complement activation** and leads to immediate graft failure [1]. *6-12 months* - Rejection occurring in this timeframe might still be acute, but the peak incidence is generally earlier. - Rejection presenting after 6 months is often categorized as **late acute rejection** or may start to transition towards signs of chronic rejection, which occurs over a longer period. *Few hours* - Rejection within a few hours could be a very early form of **acute rejection** or a delayed presentation of **hyperacute rejection** [1]. - However, the classic presentation of acute rejection is more prolonged than a few hours, usually developing over days to weeks. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 241-242.

12 Questions — Page 2 of 2

Q11

Which tumor arises from embryonic neural cells?

Q12

Acute graft rejection occurs within?

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