Laboratory Procedures & Biopsies Flashcards

Which biopsy technique is most appropriate for sampling a large, flat, pigmented lesion to assess for melanoma?

Answer: Excisional biopsy

Excisional biopsy removes the entire lesion with margins, providing complete tissue for accurate melanoma staging and Breslow depth measurement.

When performing a KOH (potassium hydroxide) preparation, what does a positive result indicate?

Answer: Fungal infection

KOH dissolves keratin, leaving fungal hyphae or spores visible under microscopy, confirming a fungal infection.

What is the correct angle for inserting a punch biopsy tool into the skin?

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.

Which fixative is the standard for preserving biopsy specimens before histopathologic analysis?

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.

A slit-skin smear is primarily used to diagnose which condition?

Answer: Leprosy

Slit-skin smears are used to detect Mycobacterium leprae in tissue fluid from incised skin sites to diagnose and classify leprosy.

What does a positive Tzanck smear demonstrate?

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).

Which specimen collection method is preferred for diagnosing onychomycosis in a nail?

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.