When you are examining a slide you hold it up to see the number of cuts and the nature of the specimen. Is it a punch, shave or excision biopsy? You should look at all the cuts but concentrate on the busiest bit!
Conditions showing epidermal pathology are usually to be found in the Red Scaly Mnemonic ie PMs PETAL (The Prime Minister's Pet a little cat called PETAL) . However pustules, vesicles and blisters can also be found in the epidermis so II for pustules and ICI for vesicles and blisters have to be invoked if these are seen either clinically or histologically.
1.
Look at the stratum corneum, orthokeratosis or parakeratosis,
Granular layer present? Any coronoid lamellae? Any signs of fungus in the stratum corneum? Any neutrophils in the stratum corneum?
2.
Is there acanthosis? Or is the epidermis thinned?
3. Do the keratinocytes have a normal morphology?
Is there nuclear and cell size variability?
Any koilocytes near the granular layer?
4. Any acantholysis?
Any vesicles or pustules intra epidermally?
5. Is the basal layer normal?
Any proliferation of abnormal melanocytes either individually or in nests?
6. Any spongiosis?
What about other cells invading into the epidermis?
7. Any sign of bodies in the epidermal cells eg Orf or Molluscum
8. Are there prominent rete ridges or dermal papillae?
9.
Any extravasation of material through the epidermis?
Subconsciously asking yourself these questions when looking at the epidermis will alert you to many diagnoses.
We will look at each of these situations and discuss their significance.