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LIVE BLOG: Beyond the Biopsy


In this live blog from the Fall SDPA conference in Atlanta, Kirk Gautier, PA-C, lectures on Beyond the Biopsy. He starts by reviewing some of the basics and then shares his pearls about KOH. Here are some of the highlights.


The skin is composed of three layers: epidermis, dermis, and subcutaneous tissue (panniculus).

  • The epidermis is formed from keratinocytes 
  • The dermis is composed of collagen produced by fibroblasts
  • The panniculus is composed of lipocytes

The Basics of Epidermis:

  • The epidermis is composed of 3 basic types of cells: keratinocytes, melanocytes, and Langerhans cells
  • Merkel cells are also found scattered in the epidermis through the body and act as slow-adapting touch receptors
  • The epidermis may be divided in to 4 ZONES (from the outermost to inner layer)

                1. Horny later (stratum Corneum) 
                2. Granular layer (stratum Granulosum)
                3. Prickle layer (stratum Spinosum)
                4. Basal layer (stratum Germinativum)

Think of the acronym “Californians like Girls in String Bikinis” to help you remember. 

(On the palms and soles there is an additional layer, the stratum lucidum, just above (BELOW) the granular layer)

The Basics of Dermis:

  • Dermis – Composed of 2 layers – Papillary and Reticular delineated by supra-papillary plexus
  • Principal component is collagen (70% of dry weight of skin)
  • Other components are Elastic fibers, and Extrafibrillar matrix (ground substance)
  • Ground Substance – non-cellular & gel-like composed of glycoproteins, proteoglycans, and hyaluronic acid
  • Papillary dermis – uppermost layer and flows along with the Rete ridges (epidermal thickenings that extend downward toward dermis)
  • Reticular dermis – composed of thick and densely packed type I collagen bundles – majority of dermis viewed microscopically

Subcutaneous Basics:

  • Panniculus (subcutaneous tissue fat) – lobules of fat cells or lipocytes separated by fibrous septa composed of collagen and large blood vessels

Epidermis Basics: 

  • Skin cells divide in the basal layer and move upward to the horny layer (avg. 28 days travel)
  • As the cells move they flatten and their nucleus disappears (keratinization)
    ? Parakeratosis – retained nuclei made during abnormal keratinization
    ? Hyperkeratosis – thickening of stratum corneum
  • Between keratinocytes there is a cement substance contained in lamellar granules that is secreted in the granular and horny layer
  • This “brick and mortar” configuration contributes to cohesion and impermeability
    ?Lamellar ichthyosis – abnormality in these lamellar granules
    ?Ichthyosis vulgaris – absent or diminished granular layer
  • Melanocytes – pigment-producing cells of the epidermis
  • Melanocytes have a ratio (dependent on location) of Melanocyte:Keratinocytes
  • Darker individuals do not have more melanocytes, only more and larger melanosomes (pigment granules) produced by the melanocyte
  • Melanin forms a barrier over the nucleus of the keratinocyte and serves a photoprotective role
    ?Vitiligo – destruction of melanocytes
    ?Albinism – can not produce melanin but normal number of melanocytes
    ?PIH – melanocytes shed all their melanosomes to papillary dermis
    ?Melanoma – malignant proliferation of melanocytes
  • Langerhans Cells – originate in bone marrow and serve as immune system gatekeeper
  • Langerhans Cells need hyaluronic acid for maturation and migration and UV exposure can deplete Langerhans Cells
  • Langerhans cells produce various cytokines (including IL-12)

Stains Used in Dermatology

  • H&E Stain – hematoxylin and eosin stain (Hematoxylin – stains the nuclei of cells blue and Eosin – stains basic structures, collagen, proteins red) does not stain Elastic Tissue
  • IF Stain – Immunofluorescence – used to look for antibodies tagged with fluorescent molecules in skin or blood (Direct: uses a single antibody for skin or Indirect: uses 2 antibodies can be used for serum)
  •  igG, igA, igM, C3, Fibrin
  • Gram Stain – stains bacterial species based on their chemical and physical properties of their cell walls
    ?Gram Positive – Purple (blue)
    ?Gram Negative – Pink (red)
  • Periodic acid Schiff (PAS) – used for fungus, basement membrane, glycogen, mucopolysaccharide and stains fibrin
  • Giemsa Stain – used for mast cell granules (purple), Leishmania (red), Histoplasma (purple), and Donavon bodies (red). Preferred in lymphoid infiltrates and leukemic infiltrates as the cytoplasmic and nuclear characters are seen clearly


Tzank is easy to make:

1. Scrape the base of a vesicle with a 10 blade (yes this does hurt).
2. Wipe the liquid and cells on a slide.
3. Immerse in t-blue 5 or 6 times.
4. Rinse the BACK side of the slide with running water.
5. Drop mineral oil on slide and put cover slip on it.

Kirk’s KOH Pearls:

1. Scrape everything!
2. You will find it when you least expect it.
3. You can bill for it.
4. Patients feel like they were really examined.
5. You look like you are smart.
6. No one bothers you when you are at the microscope.
7. It buys you time when you don’t know what you are doing.


Image: University of Liverpool

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