Neoplasia Practice Questions

Q: A tumor that is negative for CK7 and CK20 is most likely which of the following?

Prostate carcinoma. In immunohistochemistry (IHC), the combination of **Cytokeratin 7 (CK7)** and **Cytokeratin 20 (CK20)** is a fundamental diagnostic algorithm used to determine the primary site of an unknown metastatic tumor. ### **Explanation of the Correct Answer** **A. Prostate Carcinoma:** Most prostate adenocarcinomas are characteristically **CK7 negative and CK20 negative** [1]. This "double negative" profile is a high-yield diagnostic marker. To confirm prostate origin, pathologists typically use more specific markers like **PSA (Prostate Specific Antigen)** or **PSMA** [1]. ### **Analysis of Incorrect Options** * **B. Colon Carcinoma:** Classically follows a **CK7– / CK20+** pattern. This is the "signature" profile for colorectal adenocarcinoma. * **C. Urothelial Carcinoma:** Typically shows a **CK7+ / CK20+** (double positive) pattern. This helps differentiate it from prostate cancer, which often presents with similar clinical symptoms. * **D. Mesothelioma:** Characteristically **CK7+ / CK20–**. It also expresses specific markers like Calretinin and WT-1. ### **High-Yield Clinical Pearls for NEET-PG** * **CK7+/CK20– Profile:** Seen in Lung (adenocarcinoma), Breast, Thyroid, and Endometrial cancers. * **CK7–/CK20+ Profile:** Highly suggestive of Colorectal cancer and Merkel cell carcinoma. * **CK7+/CK20+ Profile:** Seen in Urothelial (Bladder), Pancreatic, and Gastric cancers. * **CK7–/CK20– Profile:** Seen in **Prostate cancer**, Renal Cell Carcinoma (RCC), and Hepatocellular Carcinoma (HCC) [1]. * **Memory Aid:** "Prostate and Kidney (RCC) are 'double negative' (7-/20-), while the Bladder (Urothelial) is 'double positive' (7+/20+)." **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Lower Urinary Tract and Male Genital System, pp. 989-994.

Q: Which of the following is NOT a tumor suppressor gene?

C-myc. ### Explanation The fundamental distinction in cancer genetics lies between **Proto-oncogenes** and **Tumor Suppressor Genes (TSGs)**. **Why C-myc is the correct answer:** **C-myc** is a **proto-oncogene**, not a tumor suppressor gene [1]. It encodes a transcription factor that promotes cell cycle progression (by activating cyclins) and cell growth [1]. When mutated or overexpressed (gain-of-function), it becomes an oncogene, leading to uncontrolled proliferation. It is classically associated with **Burkitt Lymphoma** via the **t(8;14)** translocation. **Why the other options are incorrect:** * **APC (Adenomatous Polyposis Coli):** A "Gatekeeper" TSG that downregulates the WNT signaling pathway by promoting the degradation of β-catenin. Mutations lead to Familial Adenomatous Polyposis (FAP). * **p53 (TP53):** Known as the "Guardian of the Genome," it is the most commonly mutated TSG in human cancers. It induces cell cycle arrest (via p21) or apoptosis (via BAX) in response to DNA damage. * **Rb (Retinoblastoma gene):** The "Governor of the Cell Cycle," it controls the G1/S checkpoint by sequestering the E2F transcription factor. It was the first TSG discovered, leading to Knudson’s "Two-Hit Hypothesis." **High-Yield Clinical Pearls for NEET-PG:** * **Two-Hit Hypothesis:** TSGs generally require **loss-of-function** in both alleles to promote cancer (recessive at the cellular level), whereas proto-oncogenes require only a **single "gain-of-function"** mutation (dominant). * **N-myc** is associated with Neuroblastoma; **L-myc** with Small Cell Carcinoma of the Lung. * **Li-Fraumeni Syndrome:** Germline mutation of **p53** leading to multiple diverse wheels (SBLA syndrome: Sarcoma, Breast, Leukemia, Adrenal). **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 296-297.

Q: In carcinoma of unknown primary, if the tissue marker CDX-2 is positive, what does it indicate?

Gastrointestinal cancer. **Explanation:** **CDX-2 (Caudal-type homeobox 2)** is a transcription factor essential for the development and differentiation of intestinal epithelial cells. In the context of **Carcinoma of Unknown Primary (CUP)**, CDX-2 serves as a highly specific and sensitive immunohistochemical (IHC) marker for adenocarcinomas of **gastrointestinal origin**, particularly colorectal cancer (positive in >90% of cases). It is also frequently expressed in gastric and pancreaticoduodenal malignancies. **Analysis of Options:** * **Option B (Correct):** CDX-2 is the "master regulator" of the intestinal phenotype. Its expression in a metastatic lesion strongly points toward a primary site in the GI tract (Colorectal > Gastric/Small bowel). * **Option A (Bladder):** The primary marker for Urothelial carcinoma is **GATA-3**. While some urachal adenocarcinomas may express CDX-2, it is not the standard marker for bladder cancer. * **Option C (Lung):** The hallmark markers for primary lung adenocarcinoma are **TTF-1** (Thyroid Transcription Factor-1) and **Napsin A**. * **Option D (Thyroid):** Thyroid malignancies are characterized by **TTF-1** and **Thyroglobulin** (for papillary/follicular) or **Calcitonin** (for medullary carcinoma). **High-Yield Clinical Pearls for NEET-PG:** * **CK7-/CK20+/CDX-2+:** Classic IHC profile for **Colorectal Adenocarcinoma** [1]. * **CK7+/CK20-/TTF-1+:** Classic profile for **Lung Adenocarcinoma**. * **CK7+/CK20-:** Seen in Breast, Lung, and Thyroid cancers. * **PAX-8:** Highly specific for Renal, Ovarian, and Thyroid tumors. * **SATB2:** A newer, highly specific marker for colorectal origin, often used alongside CDX-2. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Gastrointestinal Tract, pp. 819-821.

Question 1

A tumor that is negative for CK7 and CK20 is most likely which of the following?

Accepted Answer

Prostate carcinoma

Answer

Colon carcinoma

Answer

Urothelial carcinoma

Answer

Mesothelioma

Question 2

Which of the following parasitic infections predisposes to malignancies?

Accepted Answer

Schistosomiasis

Answer

Pargibunuasus

Answer

Guinea worm infection

Answer

Clonorchiasis

Question 3

Which of the following is NOT a tumor suppressor gene?

Accepted Answer

C-myc

Answer

APC

Answer

p53

Answer

Rb

Question 4

In carcinoma of unknown primary, if the tissue marker CDX-2 is positive, what does it indicate?

Accepted Answer

Gastrointestinal cancer

Answer

Bladder cancer

Answer

Lung cancer

Answer

Thyroid cancer

Question 5

Which of the following statements regarding Carcinoembryonic Antigen (CEA) is false?

Accepted Answer

Elevated only when there is hepatic metastasis

Answer

A prognostic indicator

Answer

A glycoprotein

Answer

Elevated in colorectal carcinoma

Question 6

Distinction between a poorly differentiated carcinoma and a lymphoma can be made by immunoperoxidase staining of the tumour tissue with antibodies directed against which of the following?

Accepted Answer

Cytokeratin

Answer

Desmin

Answer

Myoglobin

Answer

Vimentin

Question 7

A child is born with a single functional copy of a tumor suppressor gene. At the age of 5 years, the remaining normal allele is lost through mutation. As a result, the ability to control the transition from G1 to the S phase of the cell cycle is lost. Which of the following neoplasms is most likely to arise by means of this mechanism?

Accepted Answer

Retinoblastoma

Answer

Breast carcinoma

Answer

Adenocarcinoma of colon

Answer

Cerebral astrocytoma

Question 8

Which of the following mutations is NOT involved in tobacco-induced squamous cell carcinoma?

Accepted Answer

P16

Answer

P53

Answer

P63

Answer

NOTCH 1

Question 9

Which of the following conditions is NOT considered precancerous?

Accepted Answer

Verrucous carcinoma

Answer

Lichen planus

Answer

Submucous fibrosis

Answer

Leukoplakia

Question 10

What is the most definite feature of a malignant tumour?

Accepted Answer

Metastasis

Answer

Haemorrhage

Answer

Increased mitoses

Answer

Necrosis

Neoplasia — MCQs

Neoplasia — MCQs

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