Neuropathology — MCQs
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An 18-year-old man suffers massive trauma in a motorcycle accident. A CT scan shows multiple intracerebral hemorrhages. The patient expires after 6 months in a coma. At autopsy, there are cystic cavities within the frontal and temporal lobes, corresponding to the areas of prior hemorrhage. These cavities were formed in large measure due to the phagocytic activity of which of the following cell types?
Which of the following is the most common location of hypertensive hemorrhage?
What is the most common slowly growing vascular tumor of the spinal cord, cerebellum, and brain?
Hemangioblastoma is most commonly associated with which of the following syndromes?
Common posterior cranial fossa tumors include all of the following except?
Histologic sections from a mass originating from the meninges would most likely reveal which of the following findings?
Dürck's granuloma is seen in which organ?
Which is the most common intracranial brain tumor in adults?
Which of the following sites in the brain is a common location for ischemic damage, rabies virus infestation, and toxic damage resulting from alcohol?
A 65-year-old woman with a history of breast cancer and a recent melanoma presents to the emergency room following a tonic-clonic seizure. Blood chemistry values are within normal limits. There is no history of drug or alcohol use. MRI of the brain shows bilateral cerebral edema and a cystic, frontal lobe lesion. Frozen section obtained from a CT-guided biopsy reveals a hemorrhagic nodule of neoplastic cells. Immunohistochemical stains for which of the following antigens would be most helpful in making your diagnosis definitive for melanoma?
Neuropathology Indian Medical PG Practice Questions and MCQs
Question 141: An 18-year-old man suffers massive trauma in a motorcycle accident. A CT scan shows multiple intracerebral hemorrhages. The patient expires after 6 months in a coma. At autopsy, there are cystic cavities within the frontal and temporal lobes, corresponding to the areas of prior hemorrhage. These cavities were formed in large measure due to the phagocytic activity of which of the following cell types?
- A. Astrocytes
- B. Endothelial cells
- C. Microglial cells (Correct Answer)
- D. Neutrophils
Explanation: **Explanation:** The correct answer is **C. Microglial cells.** In the Central Nervous System (CNS), the response to injury follows a specific sequence [1]. When brain tissue undergoes necrosis (liquefactive necrosis) or hemorrhage, the debris must be cleared to allow for the formation of a cystic cavity [1]. 1. **Why Microglia are correct:** Microglial cells are the resident macrophages of the brain, derived from embryonic yolk sac macrophages (mesodermal origin) [3]. Following injury, they become activated, transform into large foamy macrophages (often called **Gitter cells**), and phagocytose lipid-rich myelin debris and hemosiderin from hemorrhages [2]. This clearance of necrotic tissue is what ultimately results in the formation of a **cystic cavity** [2]. 2. **Why other options are incorrect:** * **Astrocytes:** These are the "repair" cells of the CNS. Instead of phagocytosis, they undergo **gliosis** (hyperplasia and hypertrophy), forming a dense network of cytoplasmic processes (glial scar) that surrounds the cavity [4]. * **Endothelial cells:** These form the lining of blood vessels and the blood-brain barrier; they do not possess significant phagocytic activity. * **Neutrophils:** These are the first responders in acute inflammation (first 24–48 hours) and are involved in the initial inflammatory response, but they do not persist for months to clear debris or form chronic cystic cavities [1]. **High-Yield NEET-PG Pearls:** * **Liquefactive Necrosis:** The standard pattern of necrosis in the CNS (except for trauma-induced mechanical tearing) [1]. * **Gitter Cells:** Activated, lipid-laden microglial cells seen in areas of brain infarct or trauma [2]. * **Gliosis:** The CNS equivalent of scarring/fibrosis, mediated by astrocytes (not fibroblasts) [4]. * **Wallerian Degeneration:** Antegrade degeneration of axons following proximal injury, also cleared by microglia [4]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1268-1269. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1262-1264. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Peripheral Nerves and Skeletal Muscles, pp. 1255-1256. [4] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 697-698.
Question 142: Which of the following is the most common location of hypertensive hemorrhage?
- A. Pons
- B. Putamen (Correct Answer)
- C. Thalamus
- D. Subcortical white matter
Explanation: **Explanation:** Hypertensive intracerebral hemorrhage (ICH) is primarily caused by the rupture of small penetrating arteries (such as the lenticulostriate arteries) that have undergone **hyaline arteriolosclerosis**. This process leads to the formation of **Charcot-Bouchard microaneurysms**, which are prone to rupture under high pressure [2]. **Why Putamen is correct:** The **Putamen** (part of the basal ganglia) is the most common site for hypertensive hemorrhage, accounting for approximately **50-60%** of all cases [1]. The lenticulostriate branches of the Middle Cerebral Artery (MCA) that supply this region are particularly susceptible to the chronic shear stress of hypertension [2]. **Analysis of Incorrect Options:** * **Thalamus (Option C):** This is the second most common site (approx. 20%). Thalamic bleeds often present with sensory deficits and may extend into the third ventricle [1]. * **Pons (Option A):** This is the most common site for **brainstem** hypertensive hemorrhage [1]. It typically presents with "pinpoint pupils," quadriplegia, and rapid coma. * **Subcortical white matter (Option D):** Hemorrhages here are often referred to as "lobar hemorrhages." While they can occur in hypertension, they are more characteristically associated with **Cerebral Amyloid Angiopathy (CAA)** in elderly patients. **High-Yield Clinical Pearls for NEET-PG:** * **Order of frequency:** Putamen (most common) > Thalamus > Pons > Cerebellum (Dentate nucleus) [1]. * **Charcot-Bouchard vs. Berry Aneurysm:** Charcot-Bouchard aneurysms occur in small parenchymal vessels (hypertension/ICH), whereas Berry aneurysms occur in the Circle of Willis (Subarachnoid Hemorrhage) [3]. * **Slit Hemorrhages:** Small, old hypertensive hemorrhages that heal, leaving behind brownish, slit-like cavities containing hemosiderin-laden macrophages [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1269-1272. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Cardiovascular Disease, pp. 273-274. [3] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 705-706.
Question 143: What is the most common slowly growing vascular tumor of the spinal cord, cerebellum, and brain?
- A. Hemangioblastoma (Correct Answer)
- B. Pilocytic astrocytoma
- C. Meningioma
- D. Medulloblastoma
Explanation: ### Explanation **Hemangioblastoma** is the correct answer because it is a benign, slow-growing WHO Grade I vascular tumor that characteristically occurs in the **cerebellum (80%)**, spinal cord, and brainstem [1]. It is the most common primary intra-axial tumor of the adult cerebellum. #### Why the Correct Answer is Right: * **Pathology:** These tumors are highly vascular, consisting of thin-walled capillaries separated by "stromal cells" with vacuolated, lipid-rich cytoplasm [1]. * **Association:** While most cases are sporadic, approximately 25% are associated with **von Hippel-Lindau (VHL) disease** (Autosomal Dominant, Chromosome 3p) [1], [2]. * **Clinical Feature:** They can produce erythropoietin, leading to **secondary polycythemia**. #### Why Other Options are Incorrect: * **Pilocytic Astrocytoma:** While also a slow-growing Grade I tumor common in the cerebellum, it is a glial tumor (not vascular) and is primarily seen in children [4]. * **Meningioma:** These are common slow-growing tumors, but they are **extra-axial** (arising from arachnoid cap cells) and typically occur over the cerebral convexities rather than within the cerebellum or spinal cord parenchyma [3], [4]. * **Medulloblastoma:** This is a highly malignant (Grade IV) embryonal tumor. It is fast-growing, not slow-growing, and occurs almost exclusively in the pediatric population [4]. #### NEET-PG High-Yield Pearls: * **Imaging:** Classically appears as a **cyst with a brightly enhancing mural nodule** on MRI. * **VHL Syndrome Triad:** Hemangioblastoma (CNS + Retina), Renal Cell Carcinoma (clear cell type), and Pheochromocytoma. * **Histology Marker:** Stromal cells are positive for **Inhibin** (useful for differentiating from metastatic clear cell RCC). **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 726-727. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 724-725. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1317-1318. [4] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1319-1320.
Question 144: Hemangioblastoma is most commonly associated with which of the following syndromes?
- A. Von Hippel-Lindau syndrome (Correct Answer)
- B. Neurofibromatosis
- C. Tuberous Sclerosis
- D. Li-Fraumeni syndrome
Explanation: **Explanation:** **1. Why Von Hippel-Lindau (VHL) Syndrome is Correct:** Hemangioblastoma is a highly vascular, benign (WHO Grade 1) tumor of the central nervous system [1]. It is the hallmark lesion of **VHL syndrome**, an autosomal dominant disorder caused by a mutation in the *VHL* gene on **chromosome 3p25** [1]. While most hemangioblastomas are sporadic, approximately 25% are associated with VHL. In these patients, tumors often present at a younger age and are frequently multiple. **2. Why the Other Options are Incorrect:** * **Neurofibromatosis (NF):** NF1 is associated with optic nerve gliomas, neurofibromas, and Lisch nodules. NF2 is characterized by bilateral vestibular schwannomas, meningiomas, and ependymomas (Mnemonic: **MISME** syndrome). * **Tuberous Sclerosis (TSC):** This syndrome is associated with **Subependymal Giant Cell Astrocytoma (SEGA)**, cortical tubers, and subependymal nodules, along with systemic findings like renal angiomyolipomas [2]. * **Li-Fraumeni Syndrome:** Caused by a *TP53* mutation, it predisposes patients to a wide array of cancers, most notably sarcomas, breast cancer, and brain tumors like **medulloblastomas** or **choroid plexus carcinomas**, but not typically hemangioblastomas. **3. NEET-PG High-Yield Pearls:** * **Location:** Most common in the **cerebellum** (80%), followed by the spinal cord [1]. * **Morphology:** Classically described as a "mural nodule within a cyst" [1]. * **Histology:** Characterized by abundant thin-walled capillaries separated by neoplastic **"stromal cells"** with vacuolated, lipid-rich cytoplasm [1]. * **Paraneoplastic Syndrome:** Hemangioblastomas can produce **Erythropoietin (EPO)**, leading to secondary polycythemia. * **VHL Association:** Look for the triad of Hemangioblastoma, Renal Cell Carcinoma (clear cell type), and Pheochromocytoma. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 724-727. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1318-1319.
Question 145: Common posterior cranial fossa tumors include all of the following except?
- A. Medulloblastoma
- B. Oligodendroglioma (Correct Answer)
- C. Ependymoma
- D. Cystic astrocytoma
Explanation: **Explanation:** The posterior cranial fossa (infratentorial compartment) is the most common site for primary brain tumors in the pediatric population. The correct answer is **Oligodendroglioma** because it is characteristically a **supratentorial tumor**, typically involving the cerebral hemispheres (most commonly the frontal lobe) in adults [1]. **Analysis of Options:** * **Oligodendroglioma (Correct):** These are cortical/subcortical tumors of adults. On imaging, they often show calcification, and histologically, they feature a "fried-egg" appearance and "chicken-wire" vascularity [1]. * **Medulloblastoma:** This is the most common malignant brain tumor in children. It arises from the external granular layer of the cerebellum (roof of the 4th ventricle) in the posterior fossa [3]. * **Ependymoma:** In children, these typically arise from the floor of the 4th ventricle (posterior fossa) [2]. They are characterized by perivascular pseudorosettes [2]. * **Cystic Astrocytoma (Pilocytic Astrocytoma):** This is the most common benign brain tumor in children. It typically occurs in the cerebellum (posterior fossa) and presents as a cystic lesion with an enhancing mural nodule [4]. **High-Yield NEET-PG Pearls:** 1. **Rule of 70%:** In children, 70% of brain tumors are **infratentorial** (Posterior Fossa). In adults, 70% are **supratentorial** [4]. 2. **Common Posterior Fossa Tumors (Children):** Medulloblastoma, Pilocytic Astrocytoma, Ependymoma, and Brainstem Glioma. 3. **Oligodendroglioma Marker:** Look for **1p/19q co-deletion**, which is diagnostic and indicates a better prognosis and response to chemotherapy. 4. **Medulloblastoma Marker:** Associated with **Homer-Wright rosettes** and can spread via CSF ("drop metastasis") [3]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1311-1312. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1312-1313. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1314-1315. [4] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 725-726.
Question 146: Histologic sections from a mass originating from the meninges would most likely reveal which of the following findings?
- A. Antoni A areas and rare Verocay bodies
- B. A whorled pattern and rare psammoma bodies (Correct Answer)
- C. Endothelial proliferation and serpentine areas of necrosis
- D. "Fried-egg" appearance of tumor cells
Explanation: ### Explanation The question describes a mass originating from the **meninges**, which is the classic presentation of a **Meningioma**. These are typically benign, slow-growing tumors derived from arachnoid cap cells. **1. Why the Correct Answer is Right:** * **Whorled Pattern:** The hallmark histologic feature of meningiomas is the arrangement of tumor cells in tight, concentric clusters known as "whorls." [1] * **Psammoma Bodies:** As these whorls undergo central necrosis and dystrophic calcification, they form laminated, round calcified structures called Psammoma bodies. [1] These are particularly common in the *psammomatous* subtype of meningioma. [2] **2. Analysis of Incorrect Options:** * **Option A (Antoni A & Verocay bodies):** These are characteristic of **Schwannomas**. Antoni A refers to hypercellular areas, while Verocay bodies are rows of palisading nuclei. [1] While Schwannomas can occur in the cranial vault (e.g., CN VIII), they do not originate from the meninges. * **Option C (Endothelial proliferation & Serpentine necrosis):** These are the defining features of **Glioblastoma (GBM)**, a Grade IV astrocytoma. It is an intra-axial tumor, whereas meningiomas are extra-axial. * **Option D ("Fried-egg" appearance):** This refers to cells with central nuclei and clear halos, characteristic of **Oligodendrogliomas**. This appearance is often an artifact of slow formalin fixation. **3. NEET-PG High-Yield Pearls:** * **Location:** Most common extra-axial brain tumor in adults. * **Risk Factors:** Prior radiation and **NF2** (Neurofibromatosis type 2). [2] * **Imaging:** Shows a "Dural Tail" sign on MRI due to reactive thickening of the dura. [2] * **Receptor Status:** Often express **Progesterone Receptors**, which explains why they may enlarge during pregnancy. * **Marker:** Epithelial Membrane Antigen (EMA) positive. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 727-728. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1316-1317.
Question 147: Dürck's granuloma is seen in which organ?
- A. Spleen
- B. Heart
- C. Brain (Correct Answer)
- D. Lymph node
Explanation: **Dürck's granulomas** (also known as malarial granulomas) are a classic histopathological hallmark of **Cerebral Malaria**, caused by *Plasmodium falciparum* [1]. ### **Explanation of the Correct Answer** In cerebral malaria, parasitized red blood cells (pRBCs) adhere to the endothelial lining of cerebral capillaries (cytoadherence). This leads to microvascular obstruction, local hypoxia, and petechial hemorrhages. **Dürck's granuloma** represents the brain's reaction to these focal areas of necrosis. It consists of a central area of necrotic tissue or a small vessel surrounded by a ring of microglial cells, astrocytes, and inflammatory cells. Therefore, the **Brain** is the correct organ. ### **Why Other Options are Incorrect** * **Spleen:** While the spleen is heavily involved in malaria (splenomegaly, congestion, and presence of malarial pigment/hemozoin in Gandy-Gamna bodies), Dürck's granulomas are specific to the neuro-pathological response. * **Heart:** Myocardial involvement in malaria is rare and typically presents as non-specific interstitial edema or capillary sequestration, not granuloma formation. * **Lymph node:** Lymphadenopathy is not a primary feature of malaria, and these specific microglial nodules do not form in lymphoid tissue. ### **NEET-PG High-Yield Pearls** * **Causative Agent:** Almost exclusively seen in *Plasmodium falciparum* infection [1]. * **Pathogenesis:** Sequestration of pRBCs via **PfEMP-1** (Plasmodium falciparum erythrocyte membrane protein 1) binding to **ICAM-1** and **CD36** on vascular endothelium. * **Malarial Pigment:** Hemozoin (iron-containing pigment) is often found within the macrophages (Kupffer cells in the liver or microglial cells in the brain) in chronic cases. * **Other Brain Findings:** "Sludging" of RBCs in capillaries and "Ring hemorrhages" are also characteristic of cerebral malaria [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1274-1275.
Question 148: Which is the most common intracranial brain tumor in adults?
- A. Astrocytoma
- B. Metastasis (Correct Answer)
- C. Meningioma
- D. Oligodendroglioma
Explanation: **Explanation:** The correct answer is **Metastasis**. In adults, secondary (metastatic) tumors are significantly more common than primary brain tumors, accounting for approximately 50% of all intracranial neoplasms [1]. **1. Why Metastasis is Correct:** Metastatic spread to the brain occurs most frequently via the hematogenous route. The most common primary sources are **Lung cancer** (most common overall), followed by **Breast cancer** and **Melanoma** [1]. These tumors typically present as multiple, well-circumscribed lesions at the grey-white matter junction. **2. Analysis of Incorrect Options:** * **A. Astrocytoma:** While Glioblastoma (Grade IV Astrocytoma) is the most common **primary malignant** brain tumor in adults, it is less frequent than metastatic disease [2]. * **C. Meningioma:** This is the most common **primary benign** intracranial tumor. It arises from arachnoid cap cells and is more common in females [1]. * **D. Oligodendroglioma:** These are much rarer primary tumors, typically characterized by a "fried-egg" appearance on histology and "chicken-wire" calcifications. **3. High-Yield Clinical Pearls for NEET-PG:** * **Most common primary brain tumor (Adults):** Meningioma (Benign); Glioblastoma (Malignant) [3]. * **Most common brain tumor (Children):** Pilocytic Astrocytoma (Infratentorial) [3]. * **Location Rule:** Adult primary tumors are usually **Supratentorial**, whereas pediatric primary tumors are usually **Infratentorial** (posterior fossa) [3]. * **Radiology:** Metastases often show "ring enhancement" with significant perilesional edema on MRI. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1317-1318. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 725-726. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1319-1320.
Question 149: Which of the following sites in the brain is a common location for ischemic damage, rabies virus infestation, and toxic damage resulting from alcohol?
- A. Nucleus basalis of Meynert
- B. Purkinje cells of cerebellum (Correct Answer)
- C. Third, fifth, and sixth cortical layers of neurons in cerebral hemispheric grey matter
- D. Ammon's horn of the hippocampal gyrus
Explanation: The **Purkinje cells of the cerebellum** are among the most metabolically active and sensitive neurons in the central nervous system, making them a "vulnerability hotspot" for various insults. ### **Why Option B is Correct:** 1. **Ischemia:** Purkinje cells are highly sensitive to hypoxia (second only to the CA1 pyramidal neurons of the hippocampus). Global ischemia often leads to their selective necrosis. 2. **Rabies:** The cerebellum is a classic site for **Negri bodies** (cytoplasmic inclusions), which are frequently found within the large Purkinje cells [1]. 3. **Alcohol:** Chronic alcohol consumption leads to **alcoholic cerebellar degeneration**, specifically targeting the superior vermis and Purkinje cell layers, resulting in truncal ataxia. ### **Analysis of Incorrect Options:** * **Option A (Nucleus basalis of Meynert):** This is the primary site for cholinergic neuron loss in **Alzheimer’s disease**, not typically associated with rabies or acute ischemia. * **Option C (Cortical layers III, V, VI):** While these layers are highly sensitive to **ischemia** (laminar necrosis), they are not the characteristic site for rabies or alcohol-specific toxic damage. * **Option D (Ammon’s horn/CA1 of Hippocampus):** This is the **most sensitive** site for ischemia (Sommer’s sector) and a common site for Negri bodies in rabies [1]. However, it is not the primary target for **alcohol-induced** toxic damage, which characteristically affects the cerebellum and Wernicke-Korsakoff structures (mammillary bodies). ### **NEET-PG High-Yield Pearls:** * **Order of Ischemic Sensitivity:** Hippocampus (CA1/Ammon’s horn) > Purkinje cells > Neocortex (Layers III, V, VI). * **Negri Bodies:** Most commonly found in the **Hippocampus** (pyramidal cells) and **Cerebellum** (Purkinje cells) [1]. * **Alcoholic Triad:** Ataxia (Cerebellum), Confusion, and Ophthalmoplegia (Wernicke Encephalopathy affecting mammillary bodies). **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1279-1280.
Question 150: A 65-year-old woman with a history of breast cancer and a recent melanoma presents to the emergency room following a tonic-clonic seizure. Blood chemistry values are within normal limits. There is no history of drug or alcohol use. MRI of the brain shows bilateral cerebral edema and a cystic, frontal lobe lesion. Frozen section obtained from a CT-guided biopsy reveals a hemorrhagic nodule of neoplastic cells. Immunohistochemical stains for which of the following antigens would be most helpful in making your diagnosis definitive for melanoma?
- A. Alpha-fetoprotein
- B. HMB-45 (Correct Answer)
- C. Human chorionic gonadotropin
- D. Neuron-specific enolase
Explanation: **Explanation** The clinical presentation of a 65-year-old with a history of melanoma presenting with a new-onset seizure and a hemorrhagic, cystic brain lesion is highly suggestive of **metastatic melanoma**. Melanoma is notorious for metastasizing to the brain and frequently presents as hemorrhagic lesions on imaging [1], [3]. **Why HMB-45 is correct:** **HMB-45 (Human Melanoma Black-45)** is a highly specific monoclonal antibody that reacts against **gp100**, a cytotoxic sensory protein found in melanosomes [2]. It is a gold-standard immunohistochemical (IHC) marker for confirming the diagnosis of melanoma [2]. Other relevant markers for melanoma include **S100** (highly sensitive but less specific), **Melan-A/MART-1**, and **SOX10**. **Analysis of Incorrect Options:** * **A. Alpha-fetoprotein (AFP):** A marker for yolk sac tumors and hepatocellular carcinoma; it has no role in melanoma diagnosis. * **C. Human chorionic gonadotropin (hCG):** A marker for choriocarcinoma and certain germ cell tumors. While choriocarcinoma also causes hemorrhagic brain metastases, the patient's history specifically points toward melanoma [1]. * **D. Neuron-specific enolase (NSE):** A marker for neuroendocrine tumors (like small cell lung cancer) and certain neural tumors. While it can be positive in some melanomas, it is non-specific and less reliable than HMB-45. **High-Yield Clinical Pearls for NEET-PG:** * **Hemorrhagic Brain Metastases:** Remember the mnemonic **"CHAMP"** — **C**horiocarcinoma, **H**ypernephroma (RCC), **A**denocarcinoma (Lung/GI), **M**elanoma, and **P**heochromocytoma. * **Melanoma IHC Profile:** S100 (+), HMB-45 (+), Melan-A (+), SOX10 (+), Cytokeratin (-). * **Most common primary to metastasize to the brain:** Lung cancer > Breast cancer > Melanoma [1]. However, melanoma has the highest *propensity* to spread to the brain per case [3]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1317-1318. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Skin, pp. 1151-1152. [3] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Disorders Involving Inflammatory And Haemopoietic Cells, pp. 650-651.
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