SIAscope Training Course

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SIAscope Training Course

• Micro-architecture of skin lesions

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SIAscope training course aims

• After this course you will be able to discuss
• Common skin lesions, and their histology
• Methods of melanoma diagnosis and their relative
  merits

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Programme

• Structure of the skin
• Common lesions
• Premalignant lesions
• Melanoma

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Boundaries

• Basic structure applicable to SIAgraphs
• Melanoma
• Conditions that can be mistaken for melanoma

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Motivation

• 18 of melanomas are misdiagnosed in first
  clinical episode BJD 1999
• Difficulties of diagnosis
• Skin is a complex organ
• Many components
• Components may have strong visual resemblance to
  each other
• Different conditions can look the same

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Structure of the skin

• Epidermis
• Dermis

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Epidermis
Dermal papillae
Rete ridges
Dermis
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1.2 Histology of the skin

• Epidermis 5 layers
• Stratum corneum
• Stratum granulosum
• Dermis
• Papillary
• Reticular

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Epidermis

• Stratum Corneum (Hornlike Layer)
• 20-30 layers of dead, anucleated cells
• outer cells are constantly shed
• Stratum Lucidum (Clear Layer)
• only seen in thick skin
• 2-3 layers of dead, anucleate cells
• Stratum Granulosum (Granular Layer)
• 3-5 layers of granular, flattened cells
• Stratum Spinosum (Spiny Layer, Prickly Layer)
• several layers of polygonal-shaped cells
• Stratum Basale (Basal Layer)
• single layer of columnar/cuboidal cells resting
  on basement membrane

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Dermis Beyond

• Dermis
• Separates into papillary and reticular dermis
• Dense irregular connective tissue Collagen
• Contains nerve endings, hair follicles, glands,
  capillaries
• Dermal papillae (projections of dermal tissue
  into the epidermis) interlock with rete ridges
• Hypodermis or Superficial Fascia
• Subcutaneous tissue underneath dermis
• Stores fat and helps anchor skin

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Common lesions

• May appear similar to melanoma
• But benign
• Appearance and history important
• Junctional, Compound, Intradermal naevi
• Blue, Spindle-cell naevi
• Seborrheic Keratosis
• Pyogenic Granuloma
• Haemangioma

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Histology of skin naevi

• Normal skin

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Histology of skin lesions

• Freckles
• Seen on many people
• Junctional naevus
• Common mole

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Compound naevus

• Acquired between 6 months and 35 years
• May be raised
• Brown

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Compound naevus histology
Nests of melanocytes at rete tips
Nests of melanocytes in dermis producing less
melanin
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Compound naevus
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Blue Naevus

• Usually begin early in life
• May appear similar to nodular melanoma
• Rounded nest of melanocytes in the dermis
• Blue.

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Blue Naevus histology
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Blue Naevus
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Spitz / Spindle Cell Naevus

• Occurs mainly in children
• Smooth, round, slightly scaling pink nodule
• Very difficult to diagnose
• Resemble melanoma even in histology.

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Spitz / Spindle Cell Naevus
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Seborrhoeic Keratosis

• Acquired in middle and later life
• Slow-growing
• Scaling / stuck-on appearance

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Seborrhoeic Keratosis - Histology
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Seborrhoeic Keratosis
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Pyogenic Granuloma

• Proliferation of blood vessels

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Pyogenic granuloma
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Haemangioma

• Several kinds
• Cherry angioma can be mistaken for melanoma
• 2 to 5mm
• Red to purple in colour
• Usually on the trunk, can be multiple

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Haemangioma Histology

• Lacunes of blood

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Cherry Angioma
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Premalignant

• Lentigo maligna
• Dysplastic naevus

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Dysplastic Naevus warning!

• With or without dermal nests
• Capillary proliferation
• Increase in Collagen in dermis

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Dysplastic Naevus warning!
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Lentigo Maligna

• Precursor to lentigo maligna melanoma
• Large, cosmetically sensitive areas
• Excision undesirable in frail/elderly patients
  unless lesion changes to lentigo maligna melanoma

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Lentigo Maligna

• Punch biopsies sometimes used to confirm
  diagnosis
• Disfiguring, inaccurate
• Dermal melanin SIAgraph indicates change to
  lentigo maligna melanoma

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Lentigo Maligna
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Histology of skin lesions

• Melanoma stages
• Radial Growth Phase (RGP)
• Vertical Growth Phase (VGP)

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Histology of Melanoma
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Melanoma

• Superficial spreading melanoma (SSM)
• Nodular malignant melanoma (NMM)
• Amelanotic melanoma

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Superficial Spreading Melanoma

• Radial Growth Phase
• Microinvasion

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SSM - Histology
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Superficial Spreading melanoma
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NMM

• VGP
• Larger areas of dermal melanin

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1.2 Histology of skin lesions
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Nodular melanoma
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Amelanotic Melanoma

• Less melanin
• Very rare
• SIAscope can diagnose in theory
• No amelanotic melanomas in studies as yet

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Amelanotic melanoma
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Melanoma treatment

• Excision to fascia
• Margin based on thickness of tumour
• Up to 3cm for thick lesions
• Sentinel node biopsy(?)
• Chemotherapy, Radiation, Immunotherapy
  (interferon), Medical trials.

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Melanoma Prognosis

• Breslow thickness
• Stratum granulosum to bottom of tumour in mm
• Clarks level
• 1 in situ (epidermis)
• 2 upper papillary dermis
• 3 full thickness of papillary dermis
• 4 reticular dermis
• 5 subcutaneous fat
• Several others

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• Breslow thickness

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End of presentation

• Many different conditions may appear clinically
  similar to melanoma
• Diagnosis is difficult
• More in the next presentation