B16. Primary skin lesions, basics of dermatohistopathology

• Flat lesions
  • Macule
    • A flat skin lesion < 1 cm in size with discolouration
  • Patch
    • A flat skin lesion > 1 cm in size with discolouration
• Infiltrative lesions
  • Papule
    • An elevated palpable skin lesion < 0,5 cm in size
    • Epidermal
  • Plaque
    • An elevated palpable skin lesion > 0,5 cm in size
    • Intradermal
  • Tuber
    • An elevated palpable skin lesion whose infiltration involves the entire depth of the dermis
  • Nodule
    • A circumscribed elevated lesion > 1 cm
    • In dermis and subcutis
  • Tumor
    • Large solid mass of tissue
• Fluid-filled lesions
  • Vesicle
    • Small fluid-containing lesion
    • Intraepidermal
  • Bulla
    • Large fluid-containing lesion
    • Intraepidermal or subepidermal
  • Urtica/wheal
    • Transient oedema in the dermis
  • Pustule
    • Collection of pus in or below the epidermis
• Dermatopathological terms
  • Acantholysis
    • Separation of epidermal cells due to dissolution of desmosomes
    • E. g. in pemphigus vulgaris
  • Acanthosis
    • Hyperplasia of stratum spinosum
    • E.g. in acanthosis nigricans
  • Hypergranulosis
    • Hyperplasia of stratum granulosum
    • E.g. in lichen planus
  • Hyperkeratosis
    • Hyperplasia of stratum corneum
    • E.g. in psoriasis
  • Papillomatosis
    • Hyperplasia and enlargement of dermal papillae
  • Parakeratosis
    • Keratinocytes in stratum corneum retain their nuclei
    • E.g. in
      • Psoriasis
      • Dandruff
  • Spongiosis
    • Intraepidermal oedema
    • E.g. in
      • Atopic dermatitis
      • Allergic contact dermatitis