Dermatopathology (Part 1 of 4) Flashcards
what is the most common pigmented lesion of childhood?
freckles
when and where are freckles seen?
after sun exposure and in sun exposed areas
how do freckles change over time?
they fade and darken with season changes–> change in the degree of pigmentation
what is hyperpigmentation?
an increase in melanin pigment in basal keratinocytes
if you are seeing freckle like lesions in non-sun exposed areas, what might you be seeing?
cafe au lait spots
how are cafe au lait spots in neurofibromatosis different from freckles?
they are larger and arise independently of sun exposure; they contain aggregated melanosomes (macromalanosomes) in the cytoplasm of their melanocytes
what are malanocytes derived from?
NCCs
what is lentigo?
a benign localized hyperplasia of melanocytes–> no sex or racial predilection; cause unknown
when are lentigo’s initiated?
in infancy and childhood
how would you describe the morphological features of a lentigo?
5-10 mm, oval, tan-brown macules or patches
what happens to lentigos when they are exposed to sunlight?
nothing- they do not darken
what does a lentigo look like histologically?
linear (nonnested) melanocytic hyperplasia
where are lentigos restricted to?
restricted to the cell layer immediately above the basement membrane
what are acral sites?
palms and soles of the feet
what is the colloquial term for a melanocytic nevus?
a mole
how are melanocytic nevi acquired?
by activating mutations in components of the RAS or BRAF signaling pathway–> limited period of proliferation
what causes the proliferation seen in a melanocytic nevus to be in a permanent growth arrest?
a disruption to the p16/INK4a
what is the p16/INK4a’s function normally?
it inhibits CDK4 and CDK6
how would you describe the morphological features of a melanocytic nevus?
usually less than 6 mm, tan-brown, and uniformly pigmented; flat macules or elevated papules with well-defined borders
what are the earliest melanocytic nevi lesions known to be?
junctional nevi
what are junctional nevi?
aggregates or nests of round cells that grow along the dermoepidermal junction
what could junctional nevi progress to?
compound nevi
what are compound nevi?
nests or cords that grow into the underlying dermis (nests are in the epidermis and the dermis)
what can compound nevi progress to?
intradermal nevi
what are intradermal nevi?
there are no epidermal nests, and they are usually older lesions
which benign melanocytic nevi has the most melanin?
the more superficial one
what does the deepest evidence of a benign melanocytic nevus look like?
fusiform–> fascicles resembling neural tissue–> neurotization
what is helpful when trying to differentiate between a benign nevi and melanoma?
the metamorphosis of the nevi into something that resembles neural tissue in benign nevi
which nevi are often more elevated?
compound and dermal
which nevi are nice and flat?
junctional
what are the diagnostic architectural features of a dysplastic nevus?
coalescent intraepidermal nests
what are the cytologic features of a dysplastic nevus?
cytologic atypia
what is the clinical significance of a dysplastic nevus?
it is a potential marker or precursor of melanoma
what is dysplastic nevus syndrome?
an autosomal dominant disorder that may cause development of several melanomas at multiple sites
what gene is involved in dysplastic nevus syndrome?
CDKN2A or CDK4 gene
dysplastic nevi often acquire activating mutations in what genes?
NRAS and BRAF genes
what are the histological features of dysplastic nevi?
they are larger than acquired nevi, >5mm–> could be hundreds; variegated pigmentation, irregular borders of lesions
what are the atypical features seen in dysplastic nevi?
large nuclei, irregular angulated nuclear contour, and hyperchromasia
microscopically, dysplastic nevi usually involve what?
both the epidermis and the dermis
what is the most deadly of all skin cancers?
melanoma
what is melanoma strongly linked to?
acquired mutations caused by exposure to UV radiation in sunlight (DNA damage)
the increased incidence by decrease in death rates of melanoma may reflect what?
the effectiveness of immune checkpoint inhibitor therapy
