siascope training course micro-architecture of skin lesions
TRANSCRIPT
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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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Dermis
Epidermis
Dermal papillae
Rete ridges
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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
• Clark’s 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