SIAscope Training Course

Micro-architecture of skin lesions

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

Programme

• Structure of the skin

• Common lesions

• Premalignant lesions

• Melanoma

Boundaries

• Basic structure applicable to SIAgraphs

• Melanoma

• Conditions that can be mistaken for melanoma

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

Structure of the skin

• Epidermis

• Dermis

Dermis

Epidermis

Dermal papillae

Rete ridges

1.2 Histology of the skin

• Epidermis – 5 layers– Stratum corneum– Stratum granulosum

• Dermis– Papillary– Reticular

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

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

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

Histology of skin naevi

• Normal skin

Histology of skin lesions

• Freckles– Seen on many people

• Junctional naevus– Common “mole”

Compound naevus

• Acquired between 6 months and 35 years

• May be raised

• Brown

Compound naevus histology

Nests of melanocytes at rete tips

Nests of melanocytes in dermis producing less melanin

Compound naevus

Blue Naevus

• Usually begin early in life

• May appear similar to nodular melanoma

• Rounded nest of melanocytes in the dermis

• Blue.

Blue Naevus histology

Blue Naevus

Spitz / Spindle Cell Naevus

• Occurs mainly in children

• Smooth, round, slightly scaling pink nodule

• Very difficult to diagnose– Resemble melanoma even

in histology.

Spitz / Spindle Cell Naevus

Seborrhoeic Keratosis

• Acquired in middle and later life

• Slow-growing

• Scaling / “stuck-on” appearance

Seborrhoeic Keratosis - Histology

Seborrhoeic Keratosis

Pyogenic Granuloma

• Proliferation of blood vessels

Pyogenic granuloma

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

Haemangioma Histology

• Lacunes of blood

Cherry Angioma

Premalignant

• Lentigo maligna

• Dysplastic naevus

Dysplastic Naevus – warning!

• With or without dermal nests

• Capillary proliferation

• Increase in Collagen in dermis

Dysplastic Naevus – warning!

Lentigo Maligna

• Precursor to lentigo maligna melanoma

• Large, cosmetically sensitive areas

• Excision undesirable in frail/elderly patients unless lesion changes to lentigo maligna melanoma

Lentigo Maligna

• Punch biopsies sometimes used to confirm diagnosis

• Disfiguring, inaccurate

• Dermal melanin SIAgraph indicates change to lentigo maligna melanoma

Lentigo Maligna

Histology of skin lesions

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

Histology of Melanoma

Melanoma

• Superficial spreading melanoma (SSM)

• Nodular malignant melanoma (NMM)

• Amelanotic melanoma

Superficial Spreading Melanoma

• Radial Growth Phase

• Microinvasion

SSM - Histology

Superficial Spreading melanoma

NMM

• VGP

• Larger areas of dermal melanin

1.2 Histology of skin lesions

Nodular melanoma

Amelanotic Melanoma

• Less melanin

• Very rare

• SIAscope can diagnose in theory– No amelanotic melanomas in studies as

yet

Amelanotic melanoma

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.

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

• Breslow thickness

End of presentation

• Many different conditions may appear clinically similar to melanoma

• Diagnosis is difficult– More in the next

presentation