• Impression smears can be taken from any moist or greasy skin surface to see inflammatory, neoplastic or other cellular infiltrates, also to look for acantholytic keratinocytes, bacteria and yeasts.
• They can also be taken from cut surface of a surgical specimen or post mortem specimen.

Uses

• Suspected bacterial Skin: bacterial skin disease - overview or yeast infections Skin: mycotic disease Skin: malassezia disease.
• Non-healing wounds.
• Suspected eosinophilic granuloma complex (EGC) lesions.
• Suspected Mycobacterial infections Mycobacterium spp.
• Suspected Leishmania infections Leishmaniosis .
• Suspected neoplasia Skin: neoplasia.

Advantages

• Samples are easily and quickly taken and will allow immediate differentiation of neoplastic and infective disease in many cases.

Disadvantages

• Surface bacteria may not be causative as lesions may be contaminated.  
• Although most neoplastic lesions will exfoliate cells, some (eg sarcoma Soft tissue sarcoma) will not, so results may be erroneously negative.

Technical problems

• Impression smears will only be possible if intact skin is moist or greasy.
• Eroded skin may be secondarily infected.

Alternative techniques

• Skin biopsy Biopsy: skin with dermatohistopathology and culture.
• Fine needle aspiration Fine-needle aspirate especially if the lesion is nodular.
• Bacterial Bacteriology/fungal culture Fungal culture swab from skin surface.

Time required

Preparation

• Clip hair 1 minute.

Procedure

• 2 minutes to take samples.
• 15 minutes laboratory time to stain and examine slides.

Decision taking

Criteria for choosing test

• Eroded skin surface or eroded surface to skin mass.

Risk assessment

• Wear gloves as infections may be zoonotic.