Ancillary Studies in Cytopathology — MCQs
Which immunohistochemical marker is specific for mesothelioma?
What is the best investigation for identifying malaria species?
Fluorescence in situ hybridization (FISH) is required in which of the following interpretations of Her2/neu?
Stain used for direct microscopic examination of fungal culture is -
Which of the following is a stain for heart failure cells?
The graphical representation for flow cytometry analysis is done by which of the following?
TTF-1 (Thyroid Transcription Factor-1) immunohistochemical marker is most commonly seen in which of the following?
A patient with lytic lesions on the skull is suspected of a diagnosis of Langerhans cell histiocytosis. Which of the following is a characteristic finding on electron microscopy?
Iron in tissues is stained by:
All of the following are major subtypes of breast cancer based on Gene array analysis EXCEPT:
Ancillary Studies in Cytopathology Indian Medical PG Practice Questions and MCQs
Question 1: Which immunohistochemical marker is specific for mesothelioma?
- A. TTF-1
- B. CK7
- C. Calretinin (Correct Answer)
- D. CEA
Explanation: ***Calretinin*** - **Calretinin** is a highly sensitive and relatively specific immunohistochemical marker used to distinguish **mesothelioma** from other pulmonary or pleural malignancies [1]. - It is a **calcium-binding protein** found in mesothelial cells, making its presence a strong indicator of mesothelial origin [1]. *TTF-1* - **Thyroid transcription factor 1 (TTF-1)** is a nuclear transcription factor primarily expressed in **lung adenocarcinomas** and thyroid carcinomas. - It is used to differentiate primary lung tumors from metastatic tumors, but its presence argues against a diagnosis of mesothelioma [1]. *CK7* - **Cytokeratin 7 (CK7)** is a type of intermediate filament expressed in many epithelial tissues, including pulmonary adenocarcinomas and mesotheliomas. - While typically positive in a significant percentage of mesotheliomas, it is **not specific** because it is also positive in many adenocarcinomas, thus not distinguishing between them. *CEA* - **Carcinoembryonic antigen (CEA)** is a glycoprotein commonly expressed in **adenocarcinomas** of various origins, including lung, colorectal, breast, and gastrointestinal tracts. - **Mesotheliomas are typically negative for CEA**, making its absence a useful marker in differentiating mesothelioma from adenocarcinoma [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Lung, p. 731.
Question 2: What is the best investigation for identifying malaria species?
- A. Thick smear
- B. Thin smear with Giemsa (Correct Answer)
- C. QBC
- D. Thin smear with acridine orange
Explanation: ***Thin smear with Giemsa*** - A **thin smear** allows for the visualization of **parasite morphology** within red blood cells, which is crucial for distinguishing between species of *Plasmodium*. - **Giemsa stain** provides optimal contrast for identifying characteristic features such as **merozoites**, **trophozoites**, **schizonts**, and **gametocytes** of different malaria species. *Thick smear* - A **thick smear** is primarily used for **detecting the presence of malaria parasites** and for quantifying parasite density due to its higher sensitivity. - However, because red blood cells are lysed, it **does not preserve parasite morphology** well, making species identification difficult. *QBC* - **Quantitative Buffy Coat (QBC) analysis** is a rapid method for detecting malaria parasites based on their fluorescence under UV light. - While sensitive for detection, it generally **does not allow for precise species identification** due to the lack of clear morphological detail. *Thin smear with acridine orange* - A **thin smear stained with acridine orange** is used for rapid detection of parasites by fluorescence microscopy. - Similar to QBC, it is **less effective for detailed morphological examination** and specific species identification compared to Giemsa-stained thin smears.
Question 3: Fluorescence in situ hybridization (FISH) is required in which of the following interpretations of Her2/neu?
- A. All of the options
- B. 2+ (Correct Answer)
- C. 1+
- D. 3+
Explanation: ***Correct: 2+*** A **Her2/neu immunohistochemistry (IHC) score of 2+** is considered **equivocal**, meaning it's uncertain whether Her2/neu is overexpressed. In such cases, **Fluorescence In Situ Hybridization (FISH)** is required to determine the amplification status of the *HER2* gene, which guides treatment decisions regarding anti-HER2 therapy (trastuzumab) [1], [2]. The 2+ score shows incomplete and weak to moderate membrane staining in >10% of tumor cells, necessitating gene amplification confirmation. *Incorrect: All of the options* While FISH is crucial for equivocal interpretations, it is **not required for all** possible Her2/neu IHC results [2]. Some scores (1+ and 3+) definitively indicate Her2/neu status without requiring confirmatory testing. Routinely performing FISH for all IHC scores would be unnecessary and costly. *Incorrect: 1+* An IHC score of **1+** indicates **no Her2/neu overexpression** (faint/barely perceptible incomplete membrane staining in >10% of tumor cells). In this situation, the patient is considered **Her2-negative**, and FISH testing is **not required** as the result is clearly negative. *Incorrect: 3+* An IHC score of **3+** indicates **clear Her2/neu overexpression** (strong, complete membrane staining in >10% of tumor cells) [1]. Patients with an IHC 3+ score are considered **Her2-positive**, and typically **FISH testing is not required** to confirm this result, as the overexpression is unequivocal [2]. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 256-259. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Breast, pp. 1064-1066.
Question 4: Stain used for direct microscopic examination of fungal culture is -
- A. Gomori methenamine silver (GMS)
- B. Von kossa
- C. PAS
- D. Lactophenol cotton blue stain (Correct Answer)
Explanation: ***Lactophenol cotton blue stain*** - This is the **standard stain** for direct microscopic examination of fungal cultures and clinical specimens - The **lactophenol component** acts as a mounting fluid and killing agent, preserving fungal morphology - The **cotton blue** stains the **chitin in fungal cell walls**, making hyphae, spores, and other structures clearly visible - Widely used in **mycology laboratories** for identification of fungi based on morphological features *Gomori methenamine silver (GMS)* - GMS is a **histological stain** used to demonstrate fungi in **tissue sections**, not for direct culture examination [1] - Silver impregnation causes fungal cell walls to stain black against a green background [1] - Primarily used in **surgical pathology** for biopsy specimens [1] *Von Kossa* - This stain is used to identify **calcium salts** in tissue sections - Commonly used for visualizing bone, calcified cartilage, and pathological calcification - Not used for fungal detection *PAS (Periodic Acid-Schiff)* - PAS stains **carbohydrates and glycoproteins** and can highlight fungal elements in **tissue sections** - It is a general histological stain, not specific for direct fungal culture examination - Less specific than GMS for fungi, but useful for demonstrating fungal cell walls in tissues **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Lung, p. 717.
Question 5: Which of the following is a stain for heart failure cells?
- A. PAS
- B. Prussian blue (Correct Answer)
- C. Sudan black
- D. Oil red O
Explanation: ***Prussian blue*** - Heart failure cells are **alveolar macrophages** that have phagocytosed **hemosiderin** (iron-laden pigment) from extravasated red blood cells due to **pulmonary congestion** in heart failure. - The **Prussian blue stain** specifically detects the ferric iron (Fe3+) within hemosiderin, making it the appropriate stain for identifying heart failure cells. *PAS* - **Periodic Acid-Schiff (PAS)** stain detects **carbohydrates** such as glycogen, mucins, and glycoproteins, and is used for conditions like **glycogen storage diseases** or certain fungal infections. - It does not specifically identify iron or hemosiderin, hence it is not used for heart failure cells. *Sudan black* - **Sudan black** is a **lipid stain** used to identify intracellular **lipids** and distinguish between different types of leukemia based on the presence of myeloperoxidase. - It is not designed to detect iron or hemosiderin and thus is not used for heart failure cells. *Oil red O* - **Oil Red O** is another common stain for demonstrating neutral **lipids** and triglycerides in frozen tissue sections. - Like Sudan black, it is a lipid stain and therefore would not be helpful in identifying the iron-laden hemosiderin characteristic of heart failure cells.
Question 6: The graphical representation for flow cytometry analysis is done by which of the following?
- A. Pie chart, dot plot
- B. Histogram, dot plot (Correct Answer)
- C. Line diagram, dot plot
- D. Bar diagram, dot plot
Explanation: ***Histogram, dot plot*** - **Histograms** are used in flow cytometry to display the distribution of a single parameter (e.g., cell size, fluorescence intensity) across the cell population. - **Dot plots** are used to visualize the relationship between two or more parameters, allowing for the identification of distinct cell populations based on multiple characteristics. *Pie chart, dot plot* - **Pie charts** are typically used to represent proportions of a whole, which is not the primary way flow cytometry data is presented for detailed cell analysis. - While dot plots are correct, the combination with pie charts makes this option less accurate for typical flow cytometry analysis. *Line diagram, dot plot* - **Line diagrams** are generally used to show trends over time or continuous relationships, which is not the standard graphical representation for direct flow cytometry output. - Although dot plots are used, the inclusion of line diagrams makes this option incorrect in the context of typical flow cytometry data visualization. *Bar diagram, dot plot* - **Bar diagrams** are often used for comparing discrete categories or counting occurrences, not for displaying continuous distributions or multi-parameter relationships in flow cytometry directly. - While dot plots are correct, the pairing with bar diagrams does not represent the common and most informative graphical methods for flow cytometry analysis.
Question 7: TTF-1 (Thyroid Transcription Factor-1) immunohistochemical marker is most commonly seen in which of the following?
- A. Squamous Cell Carcinoma (SCC)
- B. Lung adenocarcinoma (Correct Answer)
- C. Large cell lung cancer
- D. Papillary thyroid carcinoma
Explanation: ***Lung adenocarcinoma*** - **TTF-1 (Thyroid Transcription Factor-1)** is a nuclear transcription factor that is highly expressed in adenocarcinomas of the lung. Positivity for TTF-1 is a key marker used in the diagnosis of primary lung adenocarcinoma, distinguishing it from other lung cancers and metastatic tumors. - While TTF-1 can also be positive in thyroid follicular and papillary carcinomas, its strong association with **lung adenocarcinoma** makes it a crucial diagnostic marker in this context, especially when differentiating between primary lung tumors and metastases or other lung cancer types. *Squamous Cell Carcinoma (SCC)* - **Squamous cell carcinoma of the lung** is generally **negative for TTF-1**. It typically expresses markers like p40 and CK5/6. - TTF-1 has very low sensitivity and specificity for squamous cell carcinoma, making it a poor choice for identifying this type of lung cancer. *Large cell lung cancer* - **Large cell lung carcinoma** is a diagnosis of exclusion and is typically **negative for TTF-1**, as well as other specific markers for adenocarcinoma or squamous cell carcinoma. - This type of cancer is characterized by large, anaplastic cells that lack features of other specific lung cancer types when viewed under a microscope. *Papillary thyroid carcinoma* - While **papillary thyroid carcinoma** is also **TTF-1 positive**, the question asks for the most common context in which TTF-1 is seen, and TTF-1 is a highly valuable marker for confirming a lung primary in the setting of lung masses. - TTF-1's utility in lung cancer diagnostics is particularly significant for differentiating primary lung adenocarcinomas from metastatic tumors and other lung cancer subtypes.
Question 8: A patient with lytic lesions on the skull is suspected of a diagnosis of Langerhans cell histiocytosis. Which of the following is a characteristic finding on electron microscopy?
- A. Eosinophils
- B. Histiocytes
- C. Birbeck granules (Correct Answer)
- D. Giant cells
Explanation: ***Birbeck granules*** - **Birbeck granules** are rod-shaped organelles with a striated core and a dilated end, resembling a "tennis racket," which are pathognomonic for **Langerhans cells** and, by extension, **Langerhans cell histiocytosis** [1]. - Their presence on **electron microscopy** is a definitive diagnostic feature for LCH [1]. *Eosinophils* - While **eosinophils** are often seen infiltrating lesions in **Langerhans cell histiocytosis**, they are not the diagnostic cellular component or ultrastructural finding on electron microscopy [1]. - **Eosinophils** are granulocytes involved in allergic reactions and parasitic infections; their appearance on EM is distinct from Birbeck granules. *Histiocytes* - **Histiocytes** (macrophages) are present in various inflammatory and neoplastic conditions and are the cell lineage from which **Langerhans cells** are derived, but their general presence on **electron microscopy** is not specific enough for diagnosing **LCH** [1]. - Without the characteristic **Birbeck granules**, a generic histiocyte would not distinguish LCH from other histiocytic disorders [1]. *Giant cells* - **Giant cells**, such as **multinucleated giant cells** or **osteoclasts**, can be found in association with bone lesions including **lytic lesions**, but they are not specific to **Langerhans cell histiocytosis** and do not possess Birbeck granules. - Their presence points to bone destruction or inflammation but not the underlying cellular pathology of LCH. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of White Blood Cells, Lymph Nodes, Spleen, and Thymus, p. 630.
Question 9: Iron in tissues is stained by:
- A. Masson's trichrome
- B. PAS
- C. Congo red
- D. Prussian blue (Correct Answer)
Explanation: ***Prussian blue*** - The **Prussian blue reaction**, also known as **Perls' stain**, specifically detects **ferric iron (Fe³⁺)** in tissues [3]. - It forms a **bright blue precipitate** (ferric ferrocyanide) when ferric iron reacts with potassium ferrocyanide in an acidic solution. *Masson's trichrome* - This stain is primarily used to differentiate **collagen fibers** from muscle fibers, which appear blue/green and red, respectively [1]. - It does not specifically stain or identify iron deposits in tissues. *PAS* - The **Periodic acid-Schiff (PAS) stain** is used to identify **carbohydrates** such as glycogen, mucosubstances, and fungal cell walls, which appear magenta. - It is not used for the detection of iron. *Congo red* - **Congo red** is a specialized stain used for identifying **amyloid deposits**, which appear pink-red and show apple-green birefringence under polarized light [2]. - It is not used for staining iron in tissues. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 25-26. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 268-269. [3] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Liver And Biliary System Disease, pp. 394-395.
Question 10: All of the following are major subtypes of breast cancer based on Gene array analysis EXCEPT:
- A. Luminal A and Luminal B
- B. Triple negative
- C. Her-2 receptor positive
- D. Estrogen receptor positive (Correct Answer)
Explanation: ***Oestrogen receptor positive*** - While **estrogen receptor (ER) positivity** is a critical prognostic and predictive marker in breast cancer, it is a single marker, not a distinct intrinsic subtype encompassing broader genomic categorization [1]. - The intrinsic subtypes are based on gene expression profiles that cluster tumors into biologically distinct groups, such as Luminal A, Luminal B, HER2-enriched, and Basal-like (including Triple Negative) [3]. *Luminal A and Luminal B* - These are major intrinsic subtypes characterized by the expression of **hormone receptors** (ER and/or PR) and differing in their proliferation rates [2]. - **Luminal A** generally has high ER, low proliferation, and a good prognosis, while **Luminal B** often has higher proliferation (e.g., higher Ki-67) and a slightly worse prognosis [2]. *Triple negative* - This is a major intrinsic subtype (**Basal-like**) defined by the absence of **estrogen receptors (ER)**, **progesterone receptors (PR)**, and **HER2 overexpression** [1], [4]. - It often correlates with a more aggressive clinical course and specific treatment approaches [4]. *Her-2 receptor positive* - This is a major intrinsic subtype characterized by the **overexpression or amplification of the HER2 gene** [3]. - These cancers are often aggressive but respond well to targeted therapies like trastuzumab [3], [4]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Breast, pp. 1064-1066. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 10th ed. The Breast, pp. 1059-1060. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Breast, p. 1060. [4] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 258-259.
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