Describe vitiligo
Partial or complete loss of melanocytes
Well demarcated macules/patches
Hand/wrist, axillae, perioral/periorbital, anogenital
Pathogenesis: autoimmune
What is albinism caused by?
it’s usually an inherited defect in tyrosinase
there is no melanin produced
in contrast to vitiligo, there are normal melanocytes in albinism, there just isn’t the enzyme necessary for normal function
What are the two general causes of pigmented lesions?
- excess melanin
- increased number of melanocytes
What are three examples of pigmented lesions due to excess melanin?
freckle
melasma
solar lentigo
What are two examples of pigmented lesions due to increased number of melanocytes?
melanocyte hyperplasia - lentigo simplex
melanocytic neoplasis - nevi, melanoma
What is the technical term for a freckle?
ephelis
ephelides
Under histology, what do freckles look like?
increased pigment in basal melanocytes
normal number of melanocytes
Describe melasma.
it’s mask-like hyperpigmentaiton on forehead and cheeks due to increased pigment transfer from melanocytes to keratinocytes
occurs in pregnancy or oral contraceptive use
usually will resolve
WHat is a solar lentigo?
a hyperpigmentation of the basal epidermis due to excess melanin production
it occurs in the elderly in areas of heavy sun exposure - it’s a protective mechanisms of the melanocytes
Describe lentigo simplex.
it’s localized hyperplasis of melanocytes
it can occur in all ages and isn’t related to sun
you get small brown macules anywhere on the skin
it results from increased number of melanocytes, resulting in increased pigment in stratum ocrneum and basal epidermis\
ITS AN EXAMPLE OF MELANOCYTIC HYPERPLASIA
In terms of skin neoplasia, what is a benign neoplasia and a malignant neoplasia
a benign neoplasm has no capability for metastasis - this includes those neoplasia that look like they COULD become metastatic, but haven’t crossed the basement membrane yet
malignant neoplasma have the potential for metastasis and have crossed the basement membrane
Is squamous cell carinoma in situ melignant or benign?
it’s still considered benign because it hasn’t crossed the basement membrane
this means it’s NOT CANCER
What are some benign neoplasia of the skin?
Melanocytic: Nevi
Epithelial: AK, adenomas
Stromal: leiomyoma, hemangioma
What are some malignant neoplasia of the skin?
Melanocytic: Melanoma
Epithelial: SCC, BCC
Stromal: DFSP, leiomyosarcoma, angiosarcoma
What are the 3 lifes stages of a nevi?
- junctional (at the junction of the epidermis and dermis - but not in the dermis yet)
- compound (in both epidermis and dermis)
- dermal (loss of the junctional part and only in the dermis)
WHat is the msot common mutatoin in a nevi?
BRAF
What’s the clinical treatment for a spitz nevus?
you have to take the whole thing off whenever you get path report saying its a spitz because they’re very hard to predict and it’s better to just remove the whole thing
Why do blue nevi look blue?
the pigmentation is deeper than in other nevi, so through the Tyndall effect and light scattering properties, they end up looking dark blue in color
they are dermal proliferations of spindled melanocytes
totally benign
WHat is a nevus of Ota
What is a nevus of Ito?
Ota - peri-ocular or intraocular dermal melanocytic nevus
ito - “mongolian spot” which is the same type of lesion as the Ota, just on the skin and not the eye
How are dysplastic nevi graded?
a pathologist will grade them based on the severity of dysplasia - how atypical they are
mild, moderate, and severe
you should excise those of moderate or severe atypia
people with multiple of these have an increased risk of melanoma
What is the only reliable way to exclude melanoma from a DD?
biopsy and get a path report
WHat are the 2 growth patterns of melanoma?
radial growth (in situ): just superficial and cannot metastasize
vertical growth: dermal invasion, formation of nodule - potential to metastasize
What gives melanoma its color variation?
a melanoma likes to spread up into the stratum corneum, but it won’t do so uniformaly, so the pigment is at varying layer sin different areas of the melanoma
What is the best predictor of a melanoma’s probability to metastasize?
breslow depth!!!!!
less than 1 mm - unlikely to metastasize
the higher the depth of penetration, the greater the liklihood of metastasis - that’s why they do a sentinel LN biopsy for melanomas with breslow depth of over 1 mm
What are some other prognistic indicators of melanoma metastasis besides breslow depth?
ulceration - more likely to metastasize
increased mitotic rate - depends on mutations
clark level (less accurate breslow)
What is a seborrheic keratosis?
it’s a very common epithelial neoplasm, typically found on the trunk, head and neck
they are brown and velvety papules/plaques, well demarcated
proliferation of keratinocytes that are pigmented - often confused for nevi or melanoma
Many on elderly patients
solar lentigo can grow into these
they cause super thick epidermis with horn cysts
What is an epithelial cst? WHat is it usually filled with?
they are down growths of epidermis which become cystic and filled with keratin
they can be subcutaneous or dermal
they rupture easily and become inflamed
What is an actinic keratosis?
it’s a benign neoplasm of epidermis (that may precede SCC)
it’s induced by sunlight, ionizing radiation or hydrocarbons
it’s a rough spot on the skin - especially sun exposed skin
It’s a form of hyperkeratosis at the basal layer
What is the treatment for actinic keratosis?
because some will progrss to squamous cell carcinoma if untreated, thy are usually treated with liquid nitrogen
What is squamous cell carcinoma?
a neoplasm of squamous cells in the skin
in situ - technically not cancer yet
SCC - has crossed the basement membrane, but only 5% will actually metastasize
mostly on elders with sun exposure
Histologically, what is the difference between an actinic keratosis and SCC?
in AK, the atypical cells are still lined up along the basement membrane
In SCC, the atypical cells have progressed and moved upward to replace the entire epidermis
What does a basal cell carcinoma typically look like?
a pearly papule with telengiectasia
they rarely metastasize
it’s the most comon human malignancy - all sun related
Adnexal neoplasms of the skin can be a clue to internal pathology, with these two syndromes as examples….
Cowden’s syndrome
Muir Torre syndrome
What is Cowden’s syndrome?
it’s a hereditary condition with a mutation in PTEN, making one prone to multiple hamartomas and malignancies
The patient will most oftne present with multiple trichilemmomas on the base (which are benign keratoses on acral skin)
while the skin ones are bening, they probably have internal carcinaoms of the breast, endometrium, and thyroid, also the cerebellar lesions
What is a trichilemmoma?
benign proliferation of hair follicle epithelial - suggestive of Cowden’s syndrome
WHat is a sebaceous hyperplasia?
it’s an acquired, localized icnrease in sebaceous glands - they will be larger than normal
it’s not neoplastic
they are common on the face
look like a yellow papule
What is Muir-Torre Syndrome?
it’s a hereditary germline mutation in DNA mistmatch repair proteins (MLH1 and MSH2)
patients will present with sebaceous adenoma and carcinoma and keratoacanthomas
Internally they will often have colon/rectlal, endometrial, and ovarian carcinaoms
it’s a subset of hereditary non-polyposis colorectal carcinoma syndrome
What is a dermatofibroma?
they are entirely benign dermal proliferation of histiocytes and fibroblasts
they are tan, brown, firm papules commonly on the legs
test with the pinch test - they’ll dimple
Where would you want to bipsy a rash?
non-ulcerated/intact skin - usually sample the center and the edge
What is the main thing to think about when biopsying discrete lesions?
how deep does it go?!
the biopsy needs to be representative in horisontal and vertical axis
When would you do a shave biopsy?
When would you do a punch biopsy?
shave for superficial lesions like BCC, AK, SCC in situ, pigmented macules. because it’s better cosmetics and you don’t need to stitch
do a punch for neoplasms involving the dermis (like nodular BCC, SCC< melanoma, etc. and most rashes), These require sutues.
What’s the difference between an incisional and excisional biopsy?
an incisional doesn’t include the entire lesion (punch is an example) and excisional does