CamScanner 07 07 2026 14.14 — Past Paper Questions & Answers

Question 1

A 52-year-old woman undergoes thyroidectomy for a well-circumscribed, encapsulated thyroid nodule. History shows uniform follicles resembling normal thyroid architecture. Which of the following is the most accurate designation?

Accepted Answer

Follicular adenoma — Follicular adenomas are benign, encapsulated thyroid nodules characterized by uniform follicles resembling normal thyroid tissue.

Question 2

A 65-year-old man is a firm mass in the sigmoid colon. Colonoscopy shows an ulcerated lesion with irregular borders. Biopsy demonstrates invasion through the muscularis propria. Which histological feature most strongly distinguishes this lesion as malignant rather than benign?

Accepted Answer

Invasion through basement membrane — Invasion of surrounding tissues, particularly beyond the basement membrane or into deeper layers like muscularis propria, is the definitive histological feature of malignancy.

Question 3

A 45-year-old woman develops chronic myeloid leukemia (CML). Cytogenetic analysis reveals a reciprocal translocation between chromosomes 9 and 22. The resultant fusion gene codes for a protein with which abnormal activity?

Accepted Answer

Constitutive non-receptor tyrosine kinase activation — The BCR-ABL fusion gene, resulting from the t(9;22) translocation in CML, produces a constitutively active non-receptor tyrosine kinase.

Question 4

A 33-year-old woman with breast cancer is found to have HER2/neu gene amplification. Which of the following best describes the mechanism by which HER2/neu promotes oncogenesis?

Accepted Answer

Overexpressed growth factor receptor causing increased proliferative signaling — HER2/neu is a growth factor receptor, and its amplification leads to overexpression, resulting in increased signaling for cell proliferation.

Question 5

A 28-year-old man presents with bilateral retinoblastomas. Genetic analysis reveals a germline mutation in one allele of the RB gene, followed by somatic loss of the second allele. This exemplifies which principle?

Accepted Answer

Knudson's two-hit hypothesis — Knudson's two-hit hypothesis describes the inactivation of both alleles of a tumor suppressor gene (one germline, one somatic) for tumor development.

Question 6

A 62-year-old man with chronic hepatitis B develops hepatocellular carcinoma. Molecular studies reveal inactivation of p53. Which of the following best describes the normal role of p53 in preventing tumor development?

Accepted Answer

Induction of apoptosis in cells with irreparable DNA damage — p53 is a tumor suppressor that induces apoptosis in cells with irreparable DNA damage, preventing the propagation of mutated cells.

Question 7

A point mutation in the RAS gene that locks it in an active GTP-bound state results in which cellular effect?

Accepted Answer

Continuous cell proliferation independent of growth factors — Constitutively active RAS signaling promotes uncontrolled cell growth and proliferation, often independent of external growth signals.

Question 8

The ERBB2 (HER2/neu) oncogene contributes to tumorigenesis primarily by:

Accepted Answer

Overexpression of a growth factor receptor — ERBB2 (HER2/neu) is a growth factor receptor, and its overexpression leads to increased proliferative signaling, contributing to tumorigenesis.

Question 9

Autocrine stimulation of growth factor receptors is best exemplified by:

Accepted Answer

Glioblastoma producing PDGF — Glioblastoma cells often produce PDGF, which then acts on their own receptors, leading to autocrine stimulation and uncontrolled growth.

Question 10

Mutation of the RB1 gene promotes cancer development by:

Accepted Answer

Removing a checkpoint that blocks G1/S transition — The RB1 gene product normally blocks the G1/S cell cycle transition; its mutation removes this checkpoint, leading to uncontrolled cell proliferation.

Question 11

Loss of function of the TGF-β signaling pathway contributes to tumorigenesis by:

Accepted Answer

Removing inhibition of cell proliferation — TGF-β normally inhibits cell proliferation; its loss of function removes this inhibitory signal, contributing to uncontrolled cell growth.

Question 12

The anti-apoptotic effect of BCL-2 overexpression in follicular lymphoma occurs due to:

Accepted Answer

Stabilization of mitochondrial membrane and inhibition of cytochrome c release — BCL-2 is an anti-apoptotic protein that prevents apoptosis by stabilizing the mitochondrial membrane and inhibiting cytochrome c release.

Question 13

Which genetic alteration would favour resistance to apoptosis?

Accepted Answer

Loss of p53 — Loss of p53 function impairs the cell's ability to initiate apoptosis in response to DNA damage, thereby promoting resistance to programmed cell death.

Question 14

Activation of telomerase contributes to cancer progression by:

Accepted Answer

Allowing indefinite cell divisions despite chromosomal shortening — Telomerase activation allows cancer cells to maintain telomere length, enabling indefinite cell divisions and cellular immortality.

Question 15

Which of the following is most directly linked to cellular senescence escape?

Accepted Answer

p16INK4a loss — p16INK4a is a tumor suppressor that enforces cellular senescence; its loss allows cells to bypass this growth arrest mechanism.

Question 16

Tumor hypoxia stimulates VEGF expression through stabilization of which transcription factor?

Accepted Answer

HIF-1α — Under hypoxic conditions, HIF-1α is stabilized and promotes the transcription of VEGF, leading to angiogenesis.

Question 17

Inhibition of angiogenesis is best achieved experimentally by blocking which pathway?

Accepted Answer

VEGF-VEGFR signaling — The VEGF-VEGFR signaling pathway is the primary driver of angiogenesis, so blocking it directly inhibits the formation of new blood vessels.

Question 18

Loss of E-cadherin expression in epithelial tumors facilitates:

Accepted Answer

Loss of cell adhesion and increased invasiveness — Loss of E-cadherin expression reduces cell-cell adhesion, facilitating tumor cell detachment, invasion, and metastasis.

Question 19

The degradation of extracellular matrix during tumor invasion is mainly mediated by:

Accepted Answer

VEGF — Matrix metalloproteinases (MMPs) are enzymes that degrade the extracellular matrix, enabling tumor cells to invade surrounding tissues.

Question 20

The Warburg effect refers to:

Accepted Answer

Preferential use of glycolysis even in presence of oxygen — The Warburg effect describes the metabolic shift in cancer cells towards increased glycolysis for energy, even when oxygen is available.

Question 21

Which molecule regulates metabolic reprogramming by promoting glycolytic enzyme expression?

Accepted Answer

MYC — MYC is an oncogene that promotes metabolic reprogramming by upregulating the expression of glycolytic enzymes, supporting rapid cell proliferation.

Question 22

Tumour cells escape immune surveillance most commonly by:

Accepted Answer

Upregulating PD-L1 expression — Tumor cells often upregulate PD-L1 to bind to PD-1 on T cells, inhibiting T cell activity and allowing the tumor to evade immune surveillance.

Question 23

Which immune cell type plays the major role in tumour immune editing and elimination?

Accepted Answer

CD8+ cytotoxic T lymphocytes — CD8+ cytotoxic T lymphocytes are crucial for recognizing and directly killing tumor cells, playing a central role in tumor immune editing and elimination.

Question 24

Defects in DNA mismatch repair genes (MLH1, MSH2) are associated with:

Accepted Answer

Hereditary nonpolyposis colorectal cancer (Lynch syndrome) — Defects in DNA mismatch repair genes like MLH1 and MSH2 are the genetic basis for Hereditary Nonpolyposis Colorectal Cancer (Lynch syndrome).

Question 25

BRCA1 and BRCA2 mutations predispose to cancer because they:

Accepted Answer

Impair homologous recombination DNA repair — BRCA1 and BRCA2 are involved in homologous recombination DNA repair; mutations impair this process, leading to genomic instability and increased cancer risk.

Question 26

Chronic Helicobacter pylori infection contributes to gastric carcinoma mainly by:

Accepted Answer

Inducing chronic inflammation and reactive oxygen species production — Chronic H. pylori infection

Question 27

Which of the following best describes the function of a proto-oncogene?

Accepted Answer

To promote normal cell growth and proliferation — Proto-oncogenes are normal genes that regulate cell growth and differentiation, and when mutated, can become oncogenes.

Question 28

A genetic disorder that manifests in some individuals who carry the disease-causing allele but not in others is an example of:

Accepted Answer

Incomplete penetrance — Incomplete penetrance occurs when individuals with a disease-causing genotype do not always express the associated phenotype.

Question 29

A tumour showing MYC amplification, VEGF overexpression, and p53 loss demonstrates which combination of hallmarks?

Accepted Answer

Only angiogenesis — MYC amplification leads to self-sufficiency in growth, p53 loss leads to resistance to death and genome instability, and VEGF overexpression leads to sustained angiogenesis.

Question 30

Which of the following is a benign tumour?

Accepted Answer

Glioblastoma — A leiomyoma is a benign tumor of smooth muscle, while the others listed are malignant.

Question 31

A 25-year-old man presents with progressive muscle weakness. Genetic testing reveals a mutation in the dystrophin gene on the X chromosome. Which best explains why this mutation leads to disease?

Accepted Answer

Defective structural protein disrupting muscle cell membrane stability — Dystrophin is a structural protein essential for maintaining the integrity of muscle cell membranes, and its defect causes muscular dystrophy.

Question 32

Which of the following is X-linked recessive?

Accepted Answer

Achondroplasia — Duchenne muscular dystrophy is a classic example of an X-linked recessive disorder.

Question 33

In X-linked recessive inheritance, carrier females:

Accepted Answer

Always show the disease — Carrier females can pass the X-linked recessive gene to their sons (who will be affected) or daughters (who will be carriers).

Question 34

Fragile X syndrome results from:

Accepted Answer

Deletion on chromosome 22q11 — Fragile X syndrome is caused by a CGG trinucleotide repeat expansion in the FMR1 gene.

Question 35

Which clinical feature is most characteristic of Fragile X syndrome?

Accepted Answer

Short stature and webbed neck — Macroorchidism (enlarged testes) and large ears are characteristic physical features of Fragile X syndrome in males.

Question 36

Genomic imprinting refers to:

Accepted Answer

Gene mutations on both alleles — Genomic imprinting is an epigenetic phenomenon where certain genes are expressed in a parent-of-origin-specific manner, often due to DNA methylation.

Question 37

Deletion of paternal chromosome 15q11-13 results in:

Accepted Answer

Angelman syndrome — Deletion of the paternal copy of chromosome 15q11-13 causes Prader-Willi syndrome.

Question 38

Deletion of the maternal 15q11-13 allele causes:

Accepted Answer

Turner syndrome — Deletion of the maternal copy of chromosome 15q11-13 causes Angelman syndrome.

Question 39

Which statement regarding mitochondrial inheritance is correct?

Accepted Answer

Affected fathers transmit to all children — Mitochondrial DNA is inherited exclusively from the mother, so affected mothers transmit the condition to all their children.

Question 40

Leber hereditary optic neuropathy (LHON) is due to:

Accepted Answer

Trisomy 13 — LHON is a mitochondrial disorder caused by mutations in mitochondrial DNA genes involved in oxidative phosphorylation.

Question 41

Which of the following features best distinguishes mitochondrial disorders from Mendelian disorders?

Accepted Answer

Variable expression and heteroplasmy — Mitochondrial disorders often exhibit variable expression and heteroplasmy (presence of both mutated and normal mitochondrial DNA within the same cell), which is less common in typical Mendelian disorders.

Question 42

A 28-year-old woman presents with pelvic pain and infertility. Laparoscopy reveals multiple blue-black lesions on the ovaries and peritoneum. Histology shows endometrial glands and stroma outside the uterus. What is the most likely diagnosis?

Accepted Answer

Adenomyosis — The presence of endometrial glands and stroma outside the uterus (blue-black lesions) is characteristic of endometriosis.

Question 43

A 35-year-old woman presents with heavy menstrual bleeding and pelvic pressure. Ultrasound reveals multiple well-circumscribed masses in the uterus composed of smooth muscle cells arranged in whorled patterns. Which diagnosis is most likely?

Accepted Answer

Endometrial carcinoma — Well-circumscribed masses of smooth muscle in the uterus, arranged in whorled patterns, are characteristic of leiomyomas (fibroids).

Question 44

A 52-year-old postmenopausal woman presents with vaginal bleeding. Endometrial biopsy shows atypical glandular proliferation with nuclear atypia. Which condition is most strongly associated with progression to endometrial carcinoma?

Accepted Answer

Simple hyperplasia without atypia — Endometrial hyperplasia with atypia carries the highest risk of progression to endometrial carcinoma among the given options.

Question 45

A 48-year-old woman presents with abnormal uterine bleeding. Histology reveals malignant glands invading the myometrium. Which risk factor is most associated with this condition?

Accepted Answer

Multiparity — Malignant glands invading the myometrium describes endometrial carcinoma, which is strongly associated with obesity due to increased estrogen production.

Question 46

A 27-year-old woman presents with amenorrhea and galactorrhea. Pregnancy test is negative. Elevated prolactin is detected. Which organ pathology is most likely responsible?

Accepted Answer

Ovary — Amenorrhea, galactorrhea, and elevated prolactin (hyperprolactinemia) are classic symptoms of a pituitary adenoma (prolactinoma).

Question 47

A 30-year-old woman presents with lower abdominal pain and positive pregnancy test. Ultrasound reveals no intrauterine pregnancy but shows a mass in the fallopian tube. Which condition is most likely?

Accepted Answer

Hydatidiform mole — A positive pregnancy test with no intrauterine pregnancy and a mass in the fallopian tube is diagnostic of an ectopic pregnancy.

Question 48

A 40-year-old woman presents with dysmenorrhea and enlarged uterus. Histology reveals endometrial glands within the myometrium. Which diagnosis is most likely?

Accepted Answer

Endometriosis — Endometrial glands and stroma within the myometrium (uterine muscle wall) is the definition of adenomyosis, which causes dysmenorrhea and an enlarged uterus.

Question 49

A 60-year-old woman presents with abdominal distension and weight loss. Imaging reveals bilateral ovarian masses. Histology shows papillary structures with psammoma bodies. Which tumour is most likely?

Accepted Answer

Serous cystadenocarcinoma — Bilateral ovarian masses with papillary structures and psammoma bodies are characteristic features of serous cystadenocarcinoma.

Question 50

A 22-year-old woman presents with abdominal pain. Imaging shows an ovarian tumour containing hair, teeth, and sebaceous material. Which tumour is most likely?

Accepted Answer

Dysgerminoma — An ovarian tumor containing differentiated tissues like hair, teeth, and sebaceous material is a mature cystic teratoma (dermoid cyst).

CamScanner 07 07 2026 14.14 — Past Paper Questions & Answers

Questions, Answers & Explanations