CDT Laboratory Procedures & Biopsies 2 — Questions and Answers
Question 1: Which biopsy technique is most appropriate for sampling a large, flat, pigmented lesion to assess for melanoma?
- Shave biopsy
- Punch biopsy
- Excisional biopsy (Correct answer)
- Curettage
Correct answer: Excisional biopsy
Excisional biopsy removes the entire lesion with margins, providing complete tissue for accurate melanoma staging and Breslow depth measurement.
Question 2: When performing a KOH (potassium hydroxide) preparation, what does a positive result indicate?
- Bacterial infection
- Viral infection
- Fungal infection (Correct answer)
- Parasitic infestation
Correct answer: Fungal infection
KOH dissolves keratin, leaving fungal hyphae or spores visible under microscopy, confirming a fungal infection.
Question 3: What is the correct angle for inserting a punch biopsy tool into the skin?
- 15 degrees to follow the skin surface
- 30 degrees angled toward the lesion center
- 45 degrees to capture deeper tissue
- 90 degrees perpendicular to the skin surface (Correct answer)
Correct answer: 90 degrees perpendicular to the skin surface
The punch biopsy tool should be inserted perpendicular (90°) to the skin surface while rotating to obtain a cylindrical core of tissue.
Question 4: Which fixative is the standard for preserving biopsy specimens before histopathologic analysis?
- Normal saline
- 70% ethanol
- 10% neutral buffered formalin (Correct answer)
- Glutaraldehyde
Correct answer: 10% neutral buffered formalin
10% neutral buffered formalin is the standard tissue fixative because it preserves cellular architecture and is compatible with most histologic stains.
Question 5: A slit-skin smear is primarily used to diagnose which condition?
- Psoriasis
- Leprosy (Correct answer)
- Pemphigus vulgaris
- Dermatitis herpetiformis
Correct answer: Leprosy
Slit-skin smears are used to detect Mycobacterium leprae in tissue fluid from incised skin sites to diagnose and classify leprosy.
Question 6: What does a positive Tzanck smear demonstrate?
- Melanocyte proliferation
- Neutrophil microabscesses
- Acantholytic cells or multinucleated giant cells (Correct answer)
- Fungal hyphae
Correct answer: Acantholytic cells or multinucleated giant cells
A positive Tzanck smear shows acantholytic cells in pemphigus or multinucleated giant cells in herpetic infections (HSV/VZV).
Question 7: Which specimen collection method is preferred for diagnosing onychomycosis in a nail?
- Swab of the nail surface
- Clipping from the distal leading edge of affected nail (Correct answer)
- Punch biopsy of the nail plate
- Shave of the proximal nail fold
Correct answer: Clipping from the distal leading edge of affected nail
Clippings from the distal leading edge of the affected nail, including subungual debris, yield the highest sensitivity for fungal culture in onychomycosis.
CDT Laboratory Procedures & Biopsies 2
Which biopsy technique is most appropriate for sampling a large, flat, pigmented lesion to assess for melanoma?