A pathologist receives a formalin-fixed paraffin-embedded (FFPE) tissue section. Which technique is most appropriate for identifying and localizing specific proteins within this section in situ?

1. A

   A. Fluorescence in situ hybridisation (FISH)

2. B

   B. Flow cytometry

3. C

   C. Western blot

4. D

   D. Immunohistochemistry (IHC)

Appeared in: INI-CET EXAM -2026

Explanation

• Immunohistochemistry (IHC) is specifically designed to identify proteins within the context of their tissue architecture.
• It utilizes the principle of specific antibody-antigen binding, where a labeled antibody binds to the target protein in the tissue section.
• The label (e.g., an enzyme like peroxidase or a fluorophore) generates a signal that can be visualized under a microscope, showing the precise location of the protein.
• This method is ideal for formalin-fixed paraffin-embedded (FFPE) samples as it maintains the morphological integrity of the tissue ('in situ').

Why Other Options Were Wrong

• Option A: This technique targets DNA or RNA sequences, not proteins.
• Option B: This method requires cells to be in a liquid suspension, which destroys the tissue's spatial structure. It cannot provide 'in situ' information.
• Option C: This technique requires homogenizing the tissue to extract proteins, which destroys the tissue architecture and loses all spatial information.

Related Visual

Clinical Relevance

• Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Molecular techniques for protein localization in tissues as background academic context rather than a clinical decision trigger.
• IHC is a cornerstone of diagnostic pathology, especially in oncology. For example, it is used to determine the expression of hormone receptors (ER/PR) and HER2 in breast cancer, which directly guides treatment decisions.
• It helps in classifying tumors, determining the cell of origin for metastatic cancers, and providing crucial prognostic information.
• What if? If the goal was to detect the presence of a specific viral DNA sequence within the cancer cells (e.g., HPV in cervical cancer), then Fluorescence In Situ Hybridization (FISH) would be the appropriate technique, not IHC.

How to Approach the Question

• First, break down the question's requirements: the target molecule is a 'protein', the sample is a 'tissue section', and the key goal is 'localization' ('in situ').
• Next, evaluate each option against these three criteria.
• Eliminate 'Fluorescence in situ hybridisation (FISH)' because its target is DNA/RNA, not protein.
• Eliminate 'Flow cytometry' because it uses cell suspensions and cannot provide 'in situ' information for a solid tissue section.
• Eliminate 'Western blot' because it requires destroying the tissue structure to extract proteins, thus losing the localization information.
• Conclude that 'Immunohistochemistry (IHC)' is the only technique that meets all criteria: it detects proteins within their original location in a tissue section.

Concept Tested & Keywords

• Concept Tested: Molecular techniques for protein localization in tissues.
• Stem keywords: formalin-fixed paraffin-embedded (FFPE), tissue section, identifying, localizing, specific proteins, in situ
• Lead-in keywords: most appropriate
• Negative lead-in flag: false

Question ID

QbhYxnFD8fgSjtxI-poOTR

Copy ID

Reference Book

E6 Textbook of Biochemistry for medical StudentsDM Vasudevan Part 2 — Subpart B (pp 240-463 of 478) p. 55-57

E6 Biochemistry U Satyanarayana— Part 2 (pp 421-820 of 840) p. 225-227