Flashcards in Disorders of Pigmentation and Melanocytes Deck (62):
What is vitiligo?
An acquired loss of pigmentation due to inflammatory destruction of melanocytes.
Who most commonly gets vitiligo?
Affects all races, however, it is most problematic in dark skinned patients.
What is the average age of onset of vitiligo?
What happens in histology of vitiligo?
Melanocytes are missing.
What is melasma?
Symmetrical hyperpigmented patches. Usually on the face and affects women with pigmented skin.
What causes melasma?
Hyperfunctioning melanocytes reacting to sun
What is post inflammatory pigment alteration?
Occurs after a variety of inflammatory and traumatic processes.
What does colour of post inflammatory pigment alteration depend on?
Colour depends on complex interplay of factors
What does histology show on post inflammatory pigment alteration?
Melanophages in superficial dermis
What is ephelis?
What triggers formation of ephelis/freckles?
Wax and wane with sun exposure
What does histology show with ephelis?
Normal epidermal architecture with increased keratinocyte pigmentation.
What is lentigo simplex?
Small flat darkly pigmented macule
What comes in fewer numbers ephelides or lentigo simplex?
Lentigo come in fewer numbers and are more darkly pigmented
What type of proliferation is lentigo simplex?
It is a melanocytic proliferation
What other growth is lentigo simplex similar to?
Junctional melanocytic naevus
What are the important histological features of lentigo simplex?
They live in the basal layer of the epidermis
They live as single cells (this differentiates them from melanocytic naevus)
They have an increased number of melanocytes
What are the clinical features of benign melanocytic naevus?
What are the histological features of common benign melanocytic naevus?
Cells predominantly in nests
Round to oval, even nuclei
Maturation as the cells get deeper
Classified as junctional, compound, and intradermal
How are benign melanocytic naevi distinguished from malignant growths?
Architectural features (Benign = cells predominantly in nests, malignant = cells grow individually and more disordered)
Cytological features (Nuclei that are crowded/overlapping, bigger than they should be, and pleiomorphic)
In naevi cells get more mature the deeper into the growth you go.
What is a spitz naevus?
A benign lesion that looks a lot like a melanoma and histologically looks like a melanoma
Which demographic commonly gets a spitz naevus?
Children and young adults
What is a blue naevus?
A dermally based benign lesion that is comprised of dendritic melanocytes
What are the melanomas that look like spitz naevi called?
What are congenital naevi?
Large, uncommon manifestation of congenital naevi
What are the issues associated with congenital naevi?
They may present significant cosmetic problems
They run a risk of developing into proliferative nodules and melanomas.
What are dysplastic naevi?
Controversial naevi that are larger than benign naevi (>6mm) with irregular borders and variable colouration.
Is the risk of dysplastic naevus becoming a melanoma high?
No, however in people that have many of them there is a higher chance of developing a melanoma especially if there is also a family history
What do dysplastic naevi look like?
Less symmetrical than benign naevi
More single cell growth
Some larger, darker nuclei
Fibrosis in upper dermis
What is done to dysplastic naevi?
Despite low risk of melanoma formation they are excised.
What is a melanoma?
Malignant tumour derived from melanocytes
Does a melanoma show up only in skin?
No, it can rarely show up in other organs.
How common is melanoma?
4th most common cancer in Australia.
1/14 males and 1/23 females are expected to develop melanoma in their lifetimes.
What is the survival rate of melanoma?
96% after 5 years if caught early
63% if there is local spread
34% if there is metastatic spread
What are the risk factors for melanoma?
Large numbers of benign or atypical naevi
Exposure to UV radiation
How is melanoma diagnosed?
What are the microscopic features of melanoma?
Single cells predominate over nests
Growth in continuity from one rete ridge to another
Extension into upper levels of epidermis
What is "buckshot" scatter?
Scatter of cells into epidermal ridges
What cytological atypia are seen in melanomas?
What is a melanoma in situ? How likely is it to metastasize?
Growth within the epidermis.
It lacks metastatic potential
until it grows out of the epidermis (no blood vessels in epidermis)
What is the radial growth phase of a melanoma? How likely is it to metastasize at this stage?
Refers to growth within epidermis as well as microinvasion into the superficial dermis. Also lacks metastatic potential.
What is the vertical growth phase of a melanoma? How likely is it to metastasize at this stage?
Invasive melanoma within the dermis that is larger than the epidermal nests. Contains mitotic figures.
This stage implies a capacity for metastatic spread.
What are the microscopic prognostic indicators for melanomas? Which factor is most important?
Tumour thickness (Breslow thickness)
Level of invasion
Lymphovascular or perineural invasion
*Breslow thickness and lymphovascular/perineural invasion are most important
What is Breslow thickness?
A ruler is used to check how deep the melanoma is.
What is the Clark level of a tumour?
Anatomical level that the melanoma has invaded into
What are the features of a superficial spreading melanoma?
Prominent epidermal component with buckshot scatter.
Does not have any implication about whether the melanoma is thin or thick.
What are the features of a nodular melanoma?
No/minimal intraepidermal component
A cutaneous metastasis needs to be excluded clinically
(Not all melanoma with a nodule is nodular melanoma)
Where is lentigo maligna melanoma seen?
Most commonly in sun damaged skin and in elderly patients.
What does a lentigo maligna melanoma look like?
Predominantly single cell growth pattern
What skin is most commonly affected by acral lentiginous melanomas?
Acral sites (i.e the hands and feet)
May occur under nails
What is the most common melanoma affecting dark skinned patients?
Acral lentiginous melanoma
Why is regression common in melanomas?
They are among the most antigenic cancers and can trigger a strong immune response which destroys cancerous cells.
Why can regression be a bad thing?
Completely regressed melanomas may explain why some patients present with metastatic melanoma but no primary tumour formation.
How are melanomas diagnosed?
Atypical pigmented lesions are biopsied with complete excision (if possible) otherwise partial biopsies are taken.
What is the problem with partial biopsies of lesions?
Less accurate and carry higher risk of misdiagnosis.
Important cause of litigation.
What is done when incomplete biopsy is taken of melanoma?
Size of lesion is included on request form.
Most clinically suspicious area is biopsied.
What mutations are common in melanomas?
BRAF, a serine-threonine kinase is mutated in 66% of melanomas.
Most mutations are located in the kinase domain
What kind of mutations in BRAF leads to melanoma?
80% are accounted for by a point mutation leading to a substitiution of glutamate for valine at position 600. V600E
What pathway does BRAF activate?
Are BRAF mutations a common cause of naevi?
Yes, they also activate the MAPK pathway but these changes are not significant enough to cause melanomas.
What is used now to treat melanomas?
Specific BRAF inhibiting drugs have been developed which are selective for V600E mutations.