A 26-year-old man has occasionally felt pain in the scrotum for the past 3 months. On physical examination, the right testis is more tender than the left but does not appear to be enlarged. An ultrasound scan shows a 1.5-cm mass within the right testis. A right orchiectomy is performed, and gross examination shows the mass to be hemorrhagic and soft. A retroperitoneal lymph node dissection is done. In sections of the lymph nodes, a neoplasm is found with extensive necrosis and hemorrhage. Microscopic examination shows that areas of viable tumors are composed of cuboidal cells intermingled with large eosinophilic syncytial cells containing multiple dark, pleomorphic nuclei. Immunohistochemical staining of syncytial cells is most likely to be positive for which of the following?
A 26-year-old man has occasionally felt pain in the scrotum for the past 3 months. On physical examination, the right testis is more tender than the left but does not appear to be enlarged. An ultrasound scan shows a 1.5-cm mass within the right testis. A right orchiectomy is performed, and gross examination shows the mass to be hemorrhagic and soft. A retroperitoneal lymph node dissection is done. In sections of the lymph nodes, a neoplasm is found with extensive necrosis and hemorrhage. Microscopic examination shows that areas of viable tumors are composed of cuboidal cells intermingled with large eosinophilic syncytial cells containing multiple dark, pleomorphic nuclei. Immunohistochemical staining of syncytial cells is most likely to be positive for which of the following?
💡 Explanation
**Core Concept**
The question is testing the student's knowledge of testicular tumors, specifically the histological features and immunohistochemical markers of choriocarcinoma, a type of germ cell tumor. Choriocarcinoma is a highly malignant tumor that can present with hemorrhage and necrosis.
**Why the Correct Answer is Right**
The presence of cuboidal cells intermingled with large eosinophilic syncytial cells containing multiple dark, pleomorphic nuclei is characteristic of choriocarcinoma. These syncytial cells are known as cytotrophoblasts, which are a hallmark of this tumor. Immunohistochemical staining of these cells is most likely to be positive for human chorionic gonadotropin (hCG), a hormone produced by the placenta during pregnancy and also by choriocarcinoma cells. hCG is a beta-subunit glycoprotein hormone that stimulates the production of testosterone and other androgens.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because hCG is not typically associated with this tumor type.
* **Option B:** This option is incorrect because hCG is not a marker for embryonal carcinoma, another type of germ cell tumor.
* **Option C:** This option is incorrect because hCG is not a marker for yolk sac tumor, a different type of germ cell tumor.
* **Option D:** This option is incorrect because hCG is not a marker for seminoma, a type of germ cell tumor that typically expresses markers such as PLAP and OCT3/4.
**Clinical Pearl / High-Yield Fact**
Choriocarcinoma is a highly malignant tumor that can present with metastatic disease, including retroperitoneal lymph node involvement. It is often associated with elevated hCG levels, which can be used as a tumor marker for diagnosis and follow-up.
**Correct Answer:**
. hCG.
✓ Correct Answer: D. Human chorionic gonadotropin
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