Neoplasia Practice Questions

Q: HMB 45 is a tumor marker for which of the following neoplasms?

Malignant melanoma. **Explanation:** **HMB-45 (Human Melanoma Black-45)** is a highly specific monoclonal antibody used in immunohistochemistry (IHC). It reacts against **gp100**, a cytotoxic transmembrane glycoprotein found in **pre-melanosomes** (specifically stages I and II). 1. **Why Malignant Melanoma is correct:** Malignant melanoma is a neoplasm of melanocytes. Since HMB-45 targets the premelanosome vesicle, it shows high positivity in melanoma cells [1]. While S-100 is more sensitive for melanoma, **HMB-45 is more specific**, making it the gold standard for confirming the diagnosis and differentiating it from other "small round blue cell tumors" or poorly differentiated carcinomas [1]. 2. **Why other options are incorrect:** * **Mesothelioma:** The characteristic markers are **Calretinin**, WT-1, and Cytokeratin 5/6. * **Bronchogenic Carcinoma:** Adenocarcinomas of the lung typically express **TTF-1** (Thyroid Transcription Factor-1) and Napsin A. * **Pancreatic Carcinoma:** These usually express CA 19-9 (serum marker) and CEA or Cytokeratins (IHC). **High-Yield Clinical Pearls for NEET-PG:** * **S-100:** Most sensitive marker for melanoma (but lacks specificity as it is also positive in neural tumors and liposarcomas). * **Melan-A (MART-1):** Another highly specific marker for melanocytic differentiation. * **SOX10:** A nuclear marker gaining popularity for its high sensitivity and specificity in spindle cell and desmoplastic melanomas. * **HMB-45 Exception:** It is also positive in **Angiomyolipoma (AML)**, as AML belongs to the PEComa (Perivascular Epithelioid Cell tumor) family. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Skin, pp. 1151-1152.

Q: With regard to the malignant behavior of leiomyosarcoma, what is the most important criterion?

The number of mitoses per high power field. In pathology, distinguishing between a benign leiomyoma and a malignant leiomyosarcoma (LMS) depends on a constellation of histological features [1]. **Why the correct answer is right:** The **mitotic count** (number of mitoses per 10 (or 50) high-power fields) is the most critical and objective parameter used to determine malignancy in smooth muscle tumors. According to the Stanford criteria, a tumor is classified as leiomyosarcoma if it exhibits: 1. **High mitotic index** (typically >10 mitoses per 10 HPF) [1]. 2. **Coagulative tumor cell necrosis.** 3. **Significant cytologic atypia.** Even in the absence of necrosis or severe atypia, a very high mitotic rate is strongly predictive of aggressive clinical behavior [1]. **Why the other options are incorrect:** * **A & B (Vascular/Lymphatic penetration):** While vascular invasion is a feature of malignancy, it is not the primary diagnostic criterion for LMS. In fact, "Intravenous Leiomyomatosis" is a benign condition where smooth muscle cells grow within vessels but do not behave as a sarcoma. * **C (Lymphocyte infiltration):** This is a non-specific inflammatory finding and does not correlate with the grade or malignant potential of smooth muscle tumors. **High-Yield NEET-PG Pearls:** * **Origin:** Leiomyosarcomas usually arise **de novo** from the myometrium, not from pre-existing leiomyomas. * **Metastasis:** Like most sarcomas, LMS spreads primarily via the **hematogenous route**, most commonly to the **lungs**. * **Demographics:** Typically occurs in postmenopausal women (unlike leiomyomas, which are estrogen-dependent and occur in younger women). * **Gross Appearance:** Look for a bulky, fleshy mass with hemorrhage and necrosis, lacking the classic "whorled" appearance of a fibroid [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Female Genital Tract, pp. 1024-1025.

Q: Which of the following terms describes a jumping gene?

Transposon. ### Explanation **Correct Option: A. Transposon** Transposons, colloquially known as **"jumping genes,"** [1] are DNA sequences that can move from one location to another within the genome. Discovered by Barbara McClintock, they play a significant role in genetic diversity and mutations. In medical pathology and microbiology, transposons are critical because they often carry genes for **antibiotic resistance** (e.g., the *vanA* gene for vancomycin resistance) and can move between bacterial chromosomes and plasmids. **Analysis of Incorrect Options:** * **B. Retroposon:** These are a specific subclass of transposons that move via an **RNA intermediate**. While they "jump," the term "Transposon" is the broader, standard definition for jumping genes. * **C. Insertion Sequence (IS):** These are the simplest type of transposable elements. They only contain the code necessary for movement (the enzyme transposase) but lack additional genes (like drug resistance) found in complex transposons. * **D. Integron:** These are genetic assembly platforms that capture and express gene cassettes. While they are mobile genetic elements, they do not "jump" by themselves; they typically rely on transposons or plasmids for movement. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** Transposons move via "cut-and-paste" or "copy-and-paste" mechanisms, often causing **insertional mutagenesis** [1] which can lead to the activation of oncogenes or inactivation of tumor suppressor genes. * **Medical Significance:** They are a primary driver of **multidrug resistance (MDR)** in hospital-acquired infections (e.g., MRSA). * **Barbara McClintock:** Awarded the Nobel Prize for discovering these elements in maize; a common trivia point in basic science sections. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. With Illustrations By, pp. 14-15.

Question 1

HMB 45 is a tumor marker for which of the following neoplasms?

Accepted Answer

Malignant melanoma

Answer

Mesothelioma

Answer

Bronchogenic carcinoma

Answer

Pancreatic carcinoma

Question 2

What is the most important feature to differentiate carcinoma in situ from invasive carcinoma?

Accepted Answer

Breach in basement membrane

Answer

Metastasis

Answer

Anaplasia

Answer

Number of mitotic spindles

Question 3

What is the most common inherited childhood tumor?

Accepted Answer

Retinoblastoma

Answer

Leukemia

Answer

Neuroblastoma

Answer

Wilms tumor

Question 4

Mucoepidermoid carcinoma arises from which cell type?

Accepted Answer

Mucin-secreting and epidermoid cells

Answer

Myothelium

Answer

Epithelium

Answer

Acinus

Question 5

With regard to the malignant behavior of leiomyosarcoma, what is the most important criterion?

Accepted Answer

The number of mitoses per high power field

Answer

Blood vessel penetration by tumor cells

Answer

Tumor cells in lymphatic channels

Answer

Lymphocyte infiltration

Question 6

Which of the following conditions is NOT associated with exposure to coal tar?

Accepted Answer

Leukemia

Answer

Bladder cancer

Answer

Skin cancer

Answer

Lung cancer

Question 7

UV radiation stimulates the formation of which of the following?

Accepted Answer

Stimulates formation of Pyrimidine dimers

Answer

Prevents formation of Pyrimidine dimers

Answer

Purine dimers

Answer

None of the above

Question 8

A child is diagnosed with neurofibromatosis type 1, characterized by cafe-au-lait spots and Lisch nodules. The protein mutated in this disorder normally performs which of the following functions?

Accepted Answer

Activates the GTPase activity of Ras

Answer

Cleaves cellular proteins during apoptosis

Answer

Functions as a cell cycle checkpoint regulator

Answer

Promotes angiogenesis

Question 9

All of the following statements are true regarding retinoblastoma, except:

Accepted Answer

The Rb gene is on chromosome 13q14.

Answer

Rb genes play a major role in cell cycle regulation.

Answer

Requires deletion of both Rb genes.

Answer

Familial variant is autosomal dominant in inheritance.

Question 10

Which of the following terms describes a jumping gene?

Accepted Answer

Transposon

Answer

Retroposon

Answer

Insertion sequence

Answer

Integron

Neoplasia — MCQs

Neoplasia — MCQs

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