Neoplasia Practice Questions

Q: The Ames test is a method for detecting which of the following?

Mutagenesis in bacteria. **Explanation:** The **Ames Test** is a rapid, high-throughput screening method used to determine the **mutagenic potential** of chemical compounds. It is based on the principle that most carcinogens are also mutagens [1]. **Why Option D is Correct:** The test utilizes a specific strain of **Salmonella typhimurium** that carries a mutation in the gene responsible for synthesizing the amino acid **histidine** (histidine auxotrophs). These bacteria cannot grow on a histidine-deficient medium. When a test chemical is added, if it is mutagenic, it induces a "back mutation" (reversion) that restores the bacteria's ability to synthesize histidine, allowing them to grow. A significant increase in colonies compared to the control indicates that the substance is a mutagen. **Why Other Options are Incorrect:** * **Options A & B:** While the Ames test is used to *screen* for potential carcinogens, it does not directly measure carcinogenesis (the formation of cancer) in rodents or primates [1]. Those require long-term, expensive *in vivo* animal bioassays. * **Option C:** Teratogenesis refers to the induction of structural defects in a fetus. The Ames test measures genetic mutations in prokaryotic cells, not developmental toxicity in mammalian embryos. **High-Yield Clinical Pearls for NEET-PG:** * **S9 Mix:** Since some chemicals only become mutagenic after being metabolized by the liver, **rat liver extract (S9 fraction)** is added to the Ames test to simulate mammalian metabolic activation. * **Correlation:** Approximately **90%** of known carcinogens test positive in the Ames test [1]. * **Other Genotoxicity Tests:** Sister Chromatid Exchange (SCE) and the Micronucleus test are used to detect chromosomal damage in mammalian cells. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 330-332.

Q: The RET proto-oncogene is located on which chromosome?

Chromosome 10. **Explanation:** The **RET (REarranged during Transfection)** proto-oncogene is located on the long arm of **Chromosome 10 (10q11.2)**. It encodes a receptor tyrosine kinase essential for the development of the neural crest-derived cells and the genitourinary system. **Why Chromosome 10 is correct:** The RET gene is a classic example of a proto-oncogene that can be activated by two distinct mechanisms: 1. **Point Mutations:** Germline mutations lead to **Multiple Endocrine Neoplasia (MEN) syndromes 2A and 2B**, as well as Familial Medullary Thyroid Carcinoma (FMTC) [1]. 2. **Gene Rearrangements:** Chromosomal translocations involving RET lead to **Papillary Thyroid Carcinoma (PTC)**, specifically the RET/PTC rearrangements [1]. **Analysis of Incorrect Options:** * **Chromosome 9:** Associated with the **ABL** proto-oncogene (involved in the t(9;22) Philadelphia chromosome in CML). * **Chromosome 11:** Home to the **WT1** (Wilms tumor) gene and the **CCND1** (Cyclin D1) gene, often involved in Mantle Cell Lymphoma via t(11;14). * **Chromosome 12:** Associated with the **KRAS** oncogene and the **MDM2** gene (often amplified in liposarcomas). **High-Yield Clinical Pearls for NEET-PG:** * **Gain-of-function** mutations in RET → MEN 2A, MEN 2B, and Medullary Thyroid Carcinoma [1]. * **Loss-of-function** mutations in RET → **Hirschsprung disease** (congenital megacolon). * **MEN 2A:** Medullary Thyroid Ca, Pheochromocytoma, Parathyroid Hyperplasia [1]. * **MEN 2B:** Medullary Thyroid Ca, Pheochromocytoma, Mucosal Neuromas, and Marfanoid habitus [1]. * Prophylactic thyroidectomy is often indicated in children carrying RET mutations to prevent aggressive Medullary Thyroid Carcinoma. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Endocrine System, pp. 1097-1137.

Q: A 58-year-old woman presents with an irregular nodularity that has developed in her right breast over the past 3 months. Mammography demonstrates irregular densities in both breasts. A needle biopsy of one breast lesion shows a certain histology, and an excisional biopsy of the contralateral breast shows similar findings. Which of the following is the most likely pathologic diagnosis?

Lobular carcinoma in situ. **Explanation:** The key to this question lies in the clinical presentation of **bilaterality** and **multicentricity**. **Why Lobular Carcinoma In Situ (LCIS) is correct:** LCIS is characterized by a proliferation of small, discohesive cells (due to loss of **E-cadherin**) filling the acini of the lobules. Unlike ductal carcinomas, LCIS is frequently **bilateral (up to 30-40% of cases)** and multicentric [1]. It is often an incidental finding because it typically does not form a distinct clinical mass or produce characteristic mammographic calcifications. In this scenario, the presence of similar lesions in both breasts strongly points toward LCIS as the most likely diagnosis. **Why the other options are incorrect:** * **Colloid (Mucinous) Carcinoma:** Usually presents as a slow-growing, circumscribed, soft/gelatinous mass in older women. It is typically unilateral. * **Malignant Phyllodes Tumor:** These are large, rapidly growing stromal tumors. While they can be aggressive, they are almost always unilateral and present as a palpable "leaf-like" mass. * **Medullary Carcinoma:** Characterized by large pleomorphic cells with a lymphoid stroma (often associated with BRCA1). It typically presents as a well-circumscribed unilateral mass. **High-Yield Clinical Pearls for NEET-PG:** * **LCIS Marker:** Loss of **E-cadherin** expression (due to CDH1 gene mutation) is the hallmark, leading to the discohesive cell pattern. * **Risk Factor:** LCIS is considered a **risk factor** (indicator) for developing invasive carcinoma in *either* breast, not necessarily a direct precursor. * **Bilateral Breast Cancer:** Whenever a question mentions bilateral or multicentric breast lesions, **Lobular** (either LCIS or Invasive Lobular Carcinoma) should be your top differential [1]. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Liver And Biliary System Disease, pp. 454-455.

Question 1

The Ames test is a method for detecting which of the following?

Accepted Answer

Mutagenesis in bacteria

Answer

Carcinogenesis in rodents

Answer

Carcinogenesis in primates

Answer

Teratogenesis in any mammalian species

Question 2

N-myc gene amplification is seen in which of the following tumors?

Accepted Answer

Neuroblastoma

Answer

Burkitt's lymphoma

Answer

Small cell lung carcinoma

Answer

All of the above

Question 3

The RET proto-oncogene is located on which chromosome?

Accepted Answer

Chromosome 10

Answer

Chromosome 9

Answer

Chromosome 11

Answer

Chromosome 12

Question 4

With reference to neoplasia, what does the term 'tumor progression' mean?

Accepted Answer

Sequential appearance of features of increasing malignancy

Answer

Spread of cancer to distant sites

Answer

Rate of growth of tumors

Answer

Ability of cancer cells to resemble their normal counterparts

Question 5

Which of the following is not considered a poor prognostic factor in neuroblastoma?

Accepted Answer

Evidence of gangliocytic differentiation

Answer

MYCN amplification

Answer

High mitosis-karyorrhexis index

Answer

Mutations of neuritogenesis genes

Question 6

Neoplastic transformation in leukoplakia is seen most commonly in which of the following locations?

Accepted Answer

Floor of mouth

Answer

Buccal mucosa

Answer

Lateral border of tongue

Answer

Palate

Question 7

Which of the following is a risk factor for bladder carcinoma?

Accepted Answer

Schistosoma hematobium

Answer

Clonorchis sinensis

Answer

Plasmodium

Answer

None of the above

Question 8

A 58-year-old woman presents with an irregular nodularity that has developed in her right breast over the past 3 months. Mammography demonstrates irregular densities in both breasts. A needle biopsy of one breast lesion shows a certain histology, and an excisional biopsy of the contralateral breast shows similar findings. Which of the following is the most likely pathologic diagnosis?

Accepted Answer

Lobular carcinoma in situ

Answer

Colloid carcinoma

Answer

Malignant phyllodes tumor

Answer

Medullary carcinoma

Question 9

The term universal tumor refers to:

Accepted Answer

Lipoma

Answer

Adenoma

Answer

Papilloma

Answer

Fibroma

Question 10

Cushing syndrome as a paraneoplastic syndrome is seen with all of the following malignancies EXCEPT:

Accepted Answer

Papillary carcinoma thyroid

Answer

Bronchial carcinoid

Answer

Thymus carcinoid

Answer

Medullary carcinoma thyroid

Neoplasia — MCQs

Neoplasia — MCQs

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