Neoplasia Practice Questions

Q: Cell-mediated lysis of tumor cells is mediated by?

HLA Class I. **Explanation:** **1. Why HLA Class I is correct:** Cell-mediated immunity against tumor cells primarily involves **CD8+ Cytotoxic T Lymphocytes (CTLs)** [1]. These T cells are specialized to recognize and kill "altered-self" cells, such as those infected by viruses or transformed into tumors. For a CTL to recognize a tumor cell, the tumor-associated antigen must be processed and presented on the cell surface in association with **HLA Class I molecules** (HLA-A, B, or C) [1]. This interaction triggers the release of perforins and granzymes, leading to apoptosis of the tumor cell. **2. Why other options are incorrect:** * **HLA Class II:** These molecules (HLA-DR, DP, DQ) are primarily expressed on **Antigen-Presenting Cells (APCs)** like dendritic cells and macrophages. They present exogenous antigens to **CD4+ Helper T cells** [1]. While CD4+ cells coordinate the immune response, they do not directly mediate the lysis of tumor cells. * **HLA Class III:** These genes encode components of the complement system (C2, C4) and certain cytokines (TNF-α). They are not involved in antigen presentation or direct T-cell recognition. **Clinical Pearls for NEET-PG:** * **Rule of 8:** Remember that MHC I × CD8 = 8 and MHC II × CD4 = 8. * **Tumor Evasion:** One common mechanism by which tumors escape immune surveillance is the **downregulation of HLA Class I expression**, making them "invisible" to CD8+ T cells. * **NK Cells:** If a tumor cell loses HLA Class I expression, it becomes a target for **Natural Killer (NK) cells**, which provide a backup defense mechanism (the "missing self" hypothesis). **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 318-319.

Q: Loss of heterozygosity is associated with which of the following conditions?

Retinoblastoma. **Explanation:** **Retinoblastoma** is the classic example of the **"Knudson Two-Hit Hypothesis."** The disease is caused by a mutation in the **RB1 gene** (a tumor suppressor gene) located on chromosome **13q14**. * In the **hereditary form**, a child inherits one defective allele (the first "hit") in all somatic cells. * Tumorigenesis occurs when the remaining functional allele in a retinal cell undergoes a somatic mutation or deletion (the second "hit"). * This transition from a heterozygous state (one normal, one mutant allele) to a state where no functional allele remains is termed **Loss of Heterozygosity (LOH)**. **Analysis of Incorrect Options:** * **A & B (AML and ALL):** While these leukemias involve complex genetic alterations (like translocations or point mutations), they are not primarily defined by the LOH mechanism seen in tumor suppressor gene-driven pediatric malignancies like Retinoblastoma. * **D (APL):** Acute Promyelocytic Leukemia is characteristically associated with a specific **balanced reciprocal translocation t(15;17)**, involving the PML and RAR-alpha genes, rather than LOH. **High-Yield Clinical Pearls for NEET-PG:** * **Most common primary intraocular tumor** in children. * **Most common presenting sign:** Leukocoria (White pupillary reflex), followed by strabismus. * **Pathology:** Flexner-Wintersteiner rosettes (highly specific) and Homer-Wright rosettes. * **Calcification:** Dystrophic calcification within the tumor is a hallmark feature on CT scans. * **Trilateral Retinoblastoma:** Bilateral retinoblastoma associated with a pinealoma (pineoblastoma).

Question 1

Which of the following is a DNA repair defect?

Accepted Answer

Bloom syndrome

Answer

Incontinentia pigmenti

Answer

Aplastic Anemia

Answer

Tuberous sclerosis

Question 2

Which of the following is an apoptosis inhibitor gene?

Accepted Answer

Bcl-2

Answer

p53

Answer

Rb

Answer

c-Myc

Question 3

A 59-year-old man complains of progressive weakness and reports very dark stools. Physical examination reveals fullness in the right lower quadrant. Laboratory studies show iron deficiency anemia (serum hemoglobin 7.4 g/dL) and stool occult blood. Colonoscopy discloses an ulcerating lesion of the cecum. Laboratory studies of the surgical specimen demonstrate hypermethylation of the p53 gene in neoplastic cells. Which of the following best characterizes this biochemical change?

Accepted Answer

Epigenetic modification

Answer

Gene amplification

Answer

Insertional mutagenesis

Answer

Nonreciprocal translocation

Question 4

All of the following are true about syndrome with microsatellite instability, except?

Accepted Answer

May be associated with immunodeficiency

Answer

DNA repair defects

Answer

Autosomal dominant

Answer

Increased risk of malignancy

Question 5

Cell-mediated lysis of tumor cells is mediated by?

Accepted Answer

HLA Class I

Answer

HLA Class II

Answer

HLA Class III

Answer

All of the above

Question 6

Elevated AFP levels are seen in all of the following conditions, EXCEPT:

Accepted Answer

Hepatoblastoma

Answer

Seminoma

Answer

Teratoma

Answer

None of the above

Question 7

Which of the following tumor suppressor genes acts by inhibition of the Hedgehog signaling pathway?

Accepted Answer

PTCH

Answer

SDHB

Answer

BRCA1

Answer

CDKN2A

Question 8

Loss of heterozygosity is associated with which of the following conditions?

Accepted Answer

Retinoblastoma

Answer

Acute myeloid leukemia

Answer

Acute lymphoblastic leukemia

Answer

Acute promyelocytic leukemia

Question 9

In which of the following tumors is alpha-fetoprotein elevated?

Accepted Answer

Hepatocellular carcinoma

Answer

Choriocarcinoma

Answer

Neuroblastoma

Answer

Seminoma

Question 10

What is the most common virus causing tumors in humans?

Accepted Answer

Human Papillomavirus (HPV)

Answer

Herpes Simplex Virus (HSV)

Answer

Epstein-Barr Virus (EBV)

Answer

Human T-lymphotropic Virus (HTLV)

Neoplasia — MCQs

Neoplasia — MCQs

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