Skin - Moles, Papules & Tumours Flashcards
What are the 5 functions of the skins?
- Protection from external insults: impermeable to prevent dehydration and prevent micro-organism entry
- Sensation
- Thermoregulation e.g. sweat glands
- Metabolic function: converts 7-dehydroxycholesterol to cholecalciferol (vit D)
- Psychosocial as diseases are obvious
What are the 3 main layers of the skin?
- Epidermis: keratinized stratified squamous epithelium on a BM
- Dermis:
- Papillary: finger-like projections (rete pegs and dermal papillae) into epidermis to allow resistance to friction
- Reticular: main part with collagen, elastin and blood vessels - Subcutis (hypodermis): store of fat and energy reserve and role in thermoregulation
What are the 3 injection routes of the skin?
- Intradermal: into skin
- Subcutaneous: subcutis
- Intramuscular: underlying muscle
What is contained within the dermis?
Epidermal appendages/adnexae e.g. hair follicles and sweat glands
How does skin get its tone and how can this be exploited in surgery to reduce scarring?
The dermis contains collagen and elastin fibres spec. in the reticular dermis that give skin tone but this degenerates with age forming wrinkles - orientation of collagen forms resting skin tension lines so incisions can be made parallel to these to reduce scarring
What forms the layers of the epidermis?
Maturing skin cells called keratinocytes (basal cells and squamous cells) - maturation of keratinocytes takes 45-60 days (~10 days in psoriasis)
What are the steps of keratinocyte maturation in the epidermis?
- BM/basal layer or germinativum/stratum basale: skin is proliferating
- Stratum spinosum/prickle cell layer: cells shrink so can see desmosomes holding them tightly together as they start to produce keratin
- Stratum granulosum: thin layer as cells flatten and mature by binding keratin fibres together and start to lose nuclei
- Stratum lucidum: some thicker skin have this additional clear layer
- Stratum corneum: cell membranes with no nuclei as cells full of keratin, membrane coated in glycophospholipid to water cells and desmosomes break down towards surface where skin sheds
Does the epidermis have its own blood supply?
No it relies on dermis
What is the pneumonic for keratinocyte maturation?
Come - Cornified Lets - Lucidum Get - Granular Sun - Spinous Burnt - Basal
What is the function of keratohyaline granules in epidermis keratinocyte maturation?
Involved in formation of keratin
What is the function of lamellar bodies in epidermis keratinocyte maturation?
Contain water repellent glycophospholipid that binds keratin flakes - key constituent of water barrier in stratum corneum
What are the 4 types of cells in the epidermis?
- Keratinocytes
- Melanocytes
- Langerhan cells
- Merkel cells
What are melanocytes? Why do they do?
Found in basal layer producing melanin with dendrites that associate with the keratinocytes around them - the melanin acts like an umbrella over basal cells nuclei to protect it from UV ray damage (malignant melanoma tends to be in fair skinned people who have less protective melanin)
What are Langerhan cells? What do they do?
Found in stratum spinosum later and involved in immune function as they have dendritic processes that take antigens, process them and present them to T-lymphocytes (can lead to type 4 hypersensitivity reaction if they start reacting to Ag which aren’t harmful to us)
What are Merkel cells? What do they do?
Typically in basal layer with a sensory function for light touch
What variations in skin are present in people?
- Additional layer of stratum lucidum in thick skin e.g. palms/soles
- Pigmented skin linked to melanin or other products e.g. karotin or bilirubin
- Vellus (thin) hairs cover most of body but some areas have terminal hair e.g. hair on head, beards
What gives rise to skin pigmentation?
No. of melanocytes fairly constant across races but type, amount and rate of breakdown is what gives rise to pigmentation
What are the 3 types of skin appendages?
- Hair follicles
- Glands
- Nails
Where are hair follicles and what do they associate with?
Found on most areas except palms, lips and soles of feet - made of keratin and associated with sebaceous glands and arrector pili smooth muscle making up the pilosebaceous unit
What are the 3 different gland types and what do they do?
- Sebaceous: produce oily sebum
- Eccrine/sweat: secrete plasma filtrate watery substance to help thermoregulation
- Apocrine: found mainly associated with hair in axilla and groin under hormonal influence - high in fat/protein so had an odour
What are nails and how are they formed?
Specialised appendage covering tip of each finger and toe where:
- Nail plate is formed by dense keratin
- Nail matrix is where nail is produced and grows
- Cuticle is thickened epidermis
Paronychia = infection of nail
What is the function of the skins circulation? What are the 2 plexuses?
Provide nutrition and thermoregulation via subpapillary (superficial) and cutaneous (deep) plexuses which anastomose so blood can flow deep or superficial depending on needs
How are skin lesions characterised?
Flat/raised
Size
Consistency
What different types of flat skin lesions exist?
- Macule = < 5mm e.g. freckle
2. Patch = > 5mm e.g. vitiligo
What different types of raised and solid skin lesions exist?
- Plaque = area > height e.g. psoriasis may have these over extensor surfaces
- Papule = < 5mm e.g. insect bite
- Nodule = > 5mm
What different types of raised fluid-filled skin lesions exist?
- Vesicles = <5mm with clear serous fluid
- Bulla = > 5mm with clear serous fluid
- Pustule = filled with pus
What is a neoplasm (tumour)?
A lesion resulting from the autonomous abnormal growth of cells that persists in the absence of an initiating stimulus - may be benign of malignant (cancer)
What are the main features of a benign skin lesion?
Growth: slow/expansive and exophytic (outward)
Appearance: symmetrical
Capsule: capsulated
Tissue type: resembles tissue of origin
Cells: differentiated
Surface: intact and smooth with circumscribed edges
What are the main features of a malignant skin lesion?
Growth: fast, invasive, metastatic and endophytic (inward)
Appearance: crab-like
Capsule: no
Tissue type: does not resemble tissue of origin
Cells: undifferentiated
Surface: irregular and infiltrative with may ulcerate/haemorrhage
What is a malignant neoplasm?
Those with characteristics that enable them to invade surrounding tissues and spread to distant sites (metastasise)
What are the 3 main types of skin cancer (malignant neoplasms) in order of most to least common?
- Basal cell carcinoma
- Squamous cell carcinoma
- Malignant melanoma
What is the key prognostic factor in skin cancers?
Thickness of lesion/depth of invasion through layers of skin via Clark levels then Breslow thickness staging
What are the risk factors for basal cell carcinoma?
UV radiation exposure
Immunosuppression
Inherited conditions e.g. xeroderma Pigmentosum and Gorlin’s syndrome
What is basal cell carcinoma?
Slow growing but does not metastasise although it is locally destructive e.g. rodent ulcer, as it is often located at sites with little surplus skin to repair the defect once it is removed so may require specialist surgery/extensive reconstruction - range of presentations e.g. superficial, nodular forms etc.
What are the risk factors for squamous cell carcinoma?
UV radiation exposure Males Fair skin Occupational exposure e.g. tars, oils and ionising radiation Immunosuppression
How does squamous cell carcinoma present?
Range of presentations but is still able to produce keratin so may have a thick crust on top of lesion
What cellular and nuclear changes can indicate malignant change?
May be seen prior to invasion in carcinoma ‘in situ’:
- Hyperchromatism
- Pleomorphism (cell and nuclei)
- High nuclear:cytoplasmic ratio
- Loss of normal tissue architecture
What do melanocytic lesions look like? What are the different types?
Pigmented usually
- Benign: naevi e.g. moles
- Borderline/unsure e.g. dysplastic/atypical
- Malignant: in situ or invasive
How do you macroscopically assess a melanocytic lesion?
A: Asymmetry B: Bordered C: Colour D: Diameter E: Evolution
As well as dermatoscopy
What are the risk factors for melanoma
UV radiation exposure
Personal or family history
Presence of dysplastic or abundant naevi
What is the difference between in situ or invasive melanoma?
In situ: nest of abnormal melanocytes within epidermis
Invasive: nest of abnormal melanocytes within epidermis AND DERMIS
What do cancer stages and grades mean?
Stage describes size of tumour and how far it has spread from where it originated
Grade describes appearance of the cancerous cell
How is melanoma staged and graded? What else might you do?
TNM (tumour, node and metastasis) staging
Testing for mutations in specific genes e.g. BRAF to see if suitable for targeted molecular therapy
What is excision biopsy?
Incision is made parallel to resting skin tension lines (RSTLs) in an ellipse shape which allows skin edges to come together easily to remove skin in someone with suspected skin cancer - size of margins (tumour-free) around lesion important is likely to be malignant
