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Pathology · single question

What type of biopsy is required to diagnose a vesiculobullous/desquamative lesion such as pemphigus or pemphigoid?

  1. An excisional biopsy of the entire lesion
  2. An incisional biopsy taken from the center of the ulcerated area
  3. A brush cytology sample
  4. A perilesional biopsy including adjacent clinically normal-appearing tissue, submitted for both routine histology and direct immunofluorescence
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Correct answer: D. A perilesional biopsy including adjacent clinically normal-appearing tissue, submitted for both routine histology and direct immunofluorescence

  • A. Excision is neither possible nor appropriate for a diffuse mucosal disease.
  • B. The ulcer center contains only necrotic debris and denuded connective tissue — a classic non-diagnostic specimen.
  • C. Brush cytology cannot demonstrate the architectural level of separation, which is the whole diagnostic point.
  • D. CORRECT. A PERILESIONAL specimen — intact epithelium immediately adjacent to the lesion — is essential. Ulcerated tissue has already lost the epithelium, so the diagnostic separation plane and the immunoreactant deposits cannot be seen. Submit TWO specimens: one in formalin for routine H&E, and one in MICHEL'S transport medium (not formalin) for direct immunofluorescence, which demonstrates the intercellular 'chicken wire' IgG pattern of pemphigus or the linear basement membrane band of pemphigoid.

Note: Formalin destroys immunoreactants. Never send the DIF specimen in formalin — use Michel's medium.

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