Skin Pathology

Question 1

What are the main histological patterns of epidermal reaction?

Answer 1

• Spongiotic (e.g. eczema)
• Psoriasiform (e.g. psoriasis)
• Bullous and pustular (e.g. impetigo, herpes simplex)
• Interface (e.g. HSP)

Question 2

What are the histological features of a spongiotic skin reaction? What diseases cause this kind of epidermal skin reaction?

Answer 2

• Oedema in epidermis and infiltrate of lymphocytes, macrophages into upper dermis
• DDx
  
  • Eczema (allergic contact dermatitis, atopic dermatitis, drug reaction)
  • Seborrhoeic dermatitis
  • Fungal infection
  • Immuno-bullous disorder

Question 3

What are the features of a psoriasiform skin reaction. What diseases cause this kind of a skin reaction?

Answer 3

• Thickening of skin (epidermis)
• DDx
  
  • Psoriasis
  • Chronic spongiotic reactions
  • AIDS-associated dermatitis
  • Prurigo nodularis (lichen simplex - chronic itching)

Question 4

Which is more likely to metastasise, BCC or SCC?

Answer 4

SCC

Question 5

What are the clinical features useful in the assessment of melanoma?

Answer 5

• Asymmetry
• Border
• Colour
• ​Depth (< 1mm denotes better prognosis)
  
  • Breslow - mm
  • Clarke - skin layers
• Evolution

Question 6

What is the most common subtype of melanoma? The next most common? Why is the latter difficult to detect?

Answer 6

• Superficial spreading melanoma (75%)
• Nodular (10%) - difficult to detect as often no irregular border or heterogenous coloured. May not be coloured.

Question 7

What are the prognostic pathological features of melanoma?

Answer 7

• Depth
• Accelerating mutations (BRAF) - molecular targeting
• Invasive mutations (PD1)
• Ulceration (may cloud depth measurement)
• Satellite lesions
• Perineural invasion