HTL Histopathology & Diagnostic Techniques 2 — Questions and Answers
Question 1: Which immunohistochemical marker is most useful for identifying neuroendocrine differentiation in a poorly differentiated carcinoma?
- Synaptophysin (Correct answer)
- Vimentin
- Desmin
- S-100
Correct answer: Synaptophysin
Synaptophysin is a pan-neuroendocrine marker expressed in neuroendocrine tumors and is highly sensitive for identifying neuroendocrine differentiation.
Question 2: In the Congo red stain for amyloid, what is the characteristic appearance under polarized light?
- Apple-green birefringence (Correct answer)
- Red-orange fluorescence
- Metachromatic purple
- Blue-black coloration
Correct answer: Apple-green birefringence
Amyloid deposits stained with Congo red exhibit apple-green birefringence under polarized light, a hallmark diagnostic feature.
Question 3: A biopsy shows cells with pale cytoplasm, perinuclear clearing, and 'raisinoid' nuclei. Which condition does this pattern suggest?
- Koilocytic change from HPV infection (Correct answer)
- Clear cell renal carcinoma
- Signet ring cell carcinoma
- Sebaceous differentiation
Correct answer: Koilocytic change from HPV infection
Koilocytes — cells with perinuclear halos and wrinkled ('raisinoid') nuclei — are the cytopathic effect of HPV infection seen in squamous epithelium.
Question 4: The Warthin-Starry stain is specifically used to identify which type of organism in tissue sections?
- Spirochetes and small gram-negative bacteria (Correct answer)
- Fungi with capsules
- Acid-fast mycobacteria
- Parasitic cysts
Correct answer: Spirochetes and small gram-negative bacteria
The Warthin-Starry silver stain visualizes spirochetes (e.g., Treponema pallidum) and small bacteria such as Helicobacter pylori and Bartonella species.
Question 5: Which histological feature best distinguishes invasive ductal carcinoma of the breast from ductal carcinoma in situ (DCIS)?
- Tumor cells penetrating through the basement membrane (Correct answer)
- High nuclear grade
- Comedonecrosis within ducts
- Mitotic figures
Correct answer: Tumor cells penetrating through the basement membrane
The defining feature of invasive carcinoma is breach of the basement membrane with tumor cells infiltrating surrounding stroma.
Question 6: A lymph node biopsy reveals effacement of normal architecture by a monotonous population of small lymphoid cells with abundant pale cytoplasm forming broad sheets. Which stain helps confirm a diagnosis of T-cell lymphoma?
- CD3 immunostain (Correct answer)
- CD20 immunostain
- Myeloperoxidase immunostain
- Cytokeratin immunostain
Correct answer: CD3 immunostain
CD3 is a pan-T-cell marker; its expression confirms T-cell lineage in lymphoid proliferations and helps distinguish T-cell from B-cell lymphomas.
Question 7: In Masson's trichrome stain, collagen fibers appear which color?
- Blue or green (Correct answer)
- Red
- Yellow
- Black
Correct answer: Blue or green
In Masson's trichrome, collagen is stained blue or green depending on the variant used, while muscle stains red and nuclei stain black.
HTL Histopathology & Diagnostic Techniques 2
Which immunohistochemical marker is most useful for identifying neuroendocrine differentiation in a poorly differentiated carcinoma?