Skin biopsies for inflammatory dermatoses

Clinical information

Provision of adequate clinical information is essential for histological assessment of suspected inflammatory dermatoses.

The clinical information should include:

• Site and duration of rash
• Distribution of the rash or specific lesions
• Clinical differential diagnosis
• Past history of similar rashes/lesions
• Relevant systemic disease
• Relevant current or previous medication (including systemic or topical treatment, such as steroids)
• Duration of treatment and, if applicable, when treatment was discontinued.
• Factors that might result in immune deficiency
• History of recent travel

Clinical images should be made available where possible.

If clinically feasible, disease modifying drugs should be withheld for 2 to 4 weeks before biopsy.

Selection of biopsy site

Selecting the appropriate site and technique of the biopsy is essential to obtain adequate and representative tissue samples for histopathological assessment.

The sampling technique should be guided by the clinical differential diagnosis. For example:

• Select a recent active lesion without secondary changes, such as excoriation and ulceration, which might result in non-specific findings

• Suspected panniculitis / large vessel vasculitis: Submit a deeper biopsy including subcutaneous adipose tissue

• For immunofluorescence of connective tissue disease, biopsies should be taken from established lesional skin (or a biopsy from sun protected, non-lesional skin for suspected lupus)

• Vasculitic lesions:
  • Biopsy an established lesion (>72 hours) for routine histology
  • Biopsy a new lesion (<24 hours) for immunofluorescence

• Immunobullous disorders:
  • A biopsy from an intact fresh vesicle or bulla is recommended for light microscopy
  • For immunofluorescence of immunobullous disorders, perilesional skin (within 5-10 mm of a lesion) is recommended

Skin biopsies should usually be sent in 10% neutral buffered formalin. Biopsies for immunofluorescence may be sent in saline or Michel’s solution.

References

Royal College of Pathologists Tissue Pathway for Dermatopathology (G075), version 3, February 2024. Link to RCPath website