Neoplasia Practice Questions

Q: The retinoblastoma gene is located on which chromosome?

Chromosome 13. ### Explanation **Correct Answer: C. Chromosome 13** The **Retinoblastoma (RB1) gene** is a classic tumor suppressor gene located on the **long arm (q) of chromosome 13**, specifically at the locus **13q14**. According to **Knudson’s "Two-Hit" Hypothesis**, both alleles of the RB1 gene must be inactivated for a tumor to develop. In the hereditary form, the first "hit" (mutation) is germline (present in all cells), and the second is somatic. In the sporadic form, both hits occur somatically within a single retinal cell. The RB1 protein (pRb) normally regulates the cell cycle by binding to the E2F transcription factor, preventing the cell from progressing from the G1 to the S phase. Loss of this "molecular brake" leads to uncontrolled cellular proliferation. **Analysis of Incorrect Options:** * **Option A (Chromosome 6):** Associated with the HLA complex and certain ocular conditions like Fuchs' endothelial dystrophy (some loci), but not the RB1 gene. * **Option B (Chromosome 9):** Notable for the ABO blood group gene and the CDKN2A gene (p16), which is involved in melanoma but not retinoblastoma. * **Option D (Chromosome 21):** Associated with Down Syndrome. Ocular findings include Brushfield spots, Keratoconus, and early-onset cataracts. **High-Yield Clinical Pearls for NEET-PG:** * **Most common intraocular malignancy** in childhood. * **Clinical Presentation:** Leukocoria (white pupillary reflex) is the most common sign, followed by strabismus. * **Histopathology:** Presence of **Flexner-Wintersteiner rosettes** (pathognomonic) and Homer Wright rosettes. * **Calcification:** A hallmark feature seen on CT scans (helps differentiate it from Coats' disease). * **Secondary Malignancy:** Patients with the hereditary form have a high risk of developing **Osteosarcoma** later in life.

Q: Which of the following is a growth factor oncogene?

Sis. **Explanation:** The correct answer is **Sis**. To understand this, we must categorize proto-oncogenes based on their functional roles in the cell signaling pathway: growth factors, receptors, signal transducers, and nuclear transcription factors. **Why 'Sis' is correct:** The **v-sis** oncogene (derived from the Simian Sarcoma Virus) encodes a protein that is nearly identical to the **Platelet-Derived Growth Factor (PDGF-β chain)**. When this gene is overexpressed, it leads to an autocrine stimulation of the cell, causing uncontrolled proliferation . It is the classic example of an oncogene acting as a **growth factor**. **Analysis of Incorrect Options:** * **MYC (Option A):** This is a **nuclear transcription factor**. The *c-MYC* oncogene is famously associated with Burkitt Lymphoma (t[8;14]). It regulates the expression of genes involved in cell cycle progression. * **Fos (Option B) & Jun (Option D):** Both *Fos* and *Jun* are **nuclear transcription factors** that dimerize to form the **AP-1 complex**. This complex binds to DNA to initiate the transcription of genes required for cell division. They act downstream of the signaling cascade, not as growth factors themselves. **High-Yield Clinical Pearls for NEET-PG:** * **Growth Factor Receptors:** *ERBB1* (EGFR) is linked to Squamous cell carcinoma of the lung; *ERBB2* (HER2/neu) is linked to Breast Cancer . * **Signal Transducers:** *RAS* (GTP-binding protein) is the most common mutated proto-oncogene in human tumors . * **Transcription Factors:** Remember the

Q: Which of the following genes promote epithelial-mesenchymal transition and are important metastatic genes in epithelial tumors?

Both SNAIL and TWIST. **Explanation:** The correct answer is **Both SNAIL and TWIST**. **1. Understanding Epithelial-Mesenchymal Transition (EMT):** EMT is a biological process where polarized epithelial cells lose their adhesion and apical-basal polarity, gaining a migratory mesenchymal phenotype. This is a critical step in the **invasion-metastasis cascade**. * **Mechanism:** The hallmark of EMT is the **downregulation of E-cadherin** (the "glue" that holds epithelial cells together) [1]. * **Role of SNAIL and TWIST:** These are specific transcription factors that act as master regulators of EMT [1]. They directly bind to the promoter of the E-cadherin gene (*CDH1*) and **repress its transcription** [1]. By suppressing E-cadherin and upregulating mesenchymal markers like Vimentin and Smooth Muscle Actin, they enable tumor cells to detach from the primary mass, breach the basement membrane, and enter the circulation. **2. Why other options are incorrect:** * **MYC (Option A):** While *MYC* is a potent proto-oncogene involved in cell cycle progression, metabolism, and transformation, it is not a primary driver of EMT. It typically promotes proliferation rather than the specific phenotypic switch to a mesenchymal state. **3. High-Yield Clinical Pearls for NEET-PG:** * **E-cadherin:** Loss of E-cadherin is the "molecular signature" of EMT and is characteristically seen in **Lobular Carcinoma of the Breast** and **Diffuse Gastric Cancer** (Signet ring cell type). * **TGF-β:** This cytokine is a major inducer of EMT in the tumor microenvironment [1]. * **Metastasis:** EMT is reversible. Once the tumor cell reaches a distant site, it undergoes **MET (Mesenchymal-Epithelial Transition)** to form a secondary colony. * **Transcription Factors:** Remember the triad of EMT regulators: **SNAIL, SLUG, and TWIST.** **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 317-318.

Question 1

Which of the following is a DNA repair defect?

Accepted Answer

Xeroderma pigmentosum

Answer

Retinoblastoma

Answer

Neurofibromatosis

Answer

MEN-I

Question 2

The retinoblastoma gene is located on which chromosome?

Accepted Answer

Chromosome 13

Answer

Chromosome 6

Answer

Chromosome 9

Answer

Chromosome 21

Question 3

All of the following malignancies metastasize except?

Accepted Answer

Basal cell carcinoma

Answer

Adenocarcinoma

Answer

Squamous cell carcinoma

Answer

Melanoma

Question 4

Which of the following is a growth factor oncogene?

Accepted Answer

Sis

Answer

MYC

Answer

Fos

Answer

Jun

Question 5

Which of the following genes promote epithelial-mesenchymal transition and are important metastatic genes in epithelial tumors?

Accepted Answer

Both SNAIL and TWIST

Answer

MYC

Answer

SNAIL

Answer

TWIST

Question 6

Which of the following is NOT a criterion for staging of a disease?

Accepted Answer

Degree of differentiation

Answer

Size of primary tumor

Answer

Extension to lymph nodes

Answer

Metastases

Question 7

Which of the following is not a carcinogenic virus?

Accepted Answer

Molluscum contagiosum

Answer

Hepatitis B

Answer

Hepatitis C

Answer

HPV

Question 8

Which of the following statements about carcinogenesis is false?

Accepted Answer

Papilloma viruses produce tumors in animals but not in humans.

Answer

Asbestos exposure increases the incidence of lung cancer.

Answer

Exposure to aniline dyes predisposes to cancer of the urinary bladder.

Answer

Hepatitis B virus has been implicated in hepatocellular carcinoma.

Question 9

The Nottingham histologic score does not include which of the following?

Accepted Answer

Presence or absence of metastases

Answer

Tubule formation

Answer

Nuclear pleomorphism

Answer

Mitotic rate

Question 10

Which type of DCIS typically presents as a palpable abnormality?

Accepted Answer

Paget's disease of the nipple

Answer

Comedocarcinoma

Answer

Non-comedo DCIS

Answer

None of the above

Neoplasia — MCQs

Neoplasia — MCQs

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