Flashcards in Dermatopathology Deck (48)
What is the function of the cornified layer of skin?
Protecting from dessication (dehydration)
Main fxn of Langerhan cells
-professional antigen presenting cells
What is the predominant cell of the epidermis
(a) 2 main functions
(a) Fxns = barrier
-also to react to pathogen invasion of the epidermis by producing proinflammatory mediators to attract leukocytes
Name the layers of the epidermis
Basal --> spinous --> granular --> cornified
What are rete ridges?
Interdigitations btwn the epidermis and dermis
-form sign wave pattern at dermal-epidermal jxn
What are merkel cells?
(a) in the basal cell layer of skin
(b) Nondendritic (not APCs), associate w/ free nerve endings to act as mechanoreceptors to help mediate touch
What are keratocanthomas?
(a) Characteristic appearance
Low grade skin tumor originating from the neck of a hair follicle
(a) Appearance = dome shaped, symmetrical, surrounded by smooth and inflamed skin
Histological features of psoriasis
-Regular elongation of rete ridges
-Perikeratosis = the silvery scale = nuclei in stratum corneum
-characteristic: find neutrophils in the cornified layer
What is perikeratosis
(a) Seen in which diseases
retention of nuclei in the stratum coreum
(a) Seen in diseases of increased cell turnover such as psoriasis and dandruff
(b) Describe process of production and packaging
Melanin = produced by melanocytes for
(a) protection from UV rays
(b) Melanin produced by melanocytes, then transported to keratinocytes where it's packaged into melanosomes
What determines skin color?
Not the number of melanocytes- that differs by body site but not by skin color
Skin color determined by the type of melanin produced (certain melanin is darker than others) and by the shape of the melanosome (spherical, ovoid) that the melanin is packaged in
Histological description of melanoma
Sheets of nested neoplastic melanocytes- large nuclei w/ prominent nucleoli (high N:C ratio)
(a) what is it
(c) biopsy features
(a) Symmetrical depigmentation
(b) Autoimmune- lymphocytes target and destroy melanocytes
(c) on biopsy see complete absence of melanocytes
Absence of pigment due to defect in melanin production
What is the most common cutaneous T cell lymphoma?
Describe the skin findings of mycosis fungoides
(a) Histological findign
Mycosis fungoides = most common cutaneous T cell lymphoma
fine scale --> plaque --> tumors
(a) Histologically: see tons of malignant lymphocytes in the epidermis
Describe the structure of the basement membrane of skin
Complex acellular basement membrane: tons of proteoglycans
Lamina lucida transversed by laminin V anchoring filaments that attach to the lamina densea (type IV collagen). Then under the lamina densa is collagen VII anchoring fibrils to the underlying dermis
Lamina lucida (laminin V) --> lamina densa (collage IV) --> collagen VII anchoring to dermis
What is bullous pemphigoid?
Acquired (congenital) blistering disease
-disease of the skin basement membrane
(a) Circulating IgG targeting antigen in the lamina lucida
(b) See separation at the epidermal-dermal junction: see the epidermis lifting off the dermis
(c) Clinically: flacid bullae that may erode
(a) mutation in collagen VII (need to anchor the lamina densa to underlying dermis)
(b) clinically get repeated erosion and scarring => loss of barrier function => frequently succumb to infection
-mitten deformity due to scarring on hands
What are adnexa of the skin?
Adnexa = appendages derived from an epidermal component
ex: hair, sweat, mammary glands, nails
What is lanugo?
Lanugo = fine hairs ubiquitous on a fetus, get replaced by vellus hair
Differentiate vellus and terminal hairs
Vellus hairs: thin, lack a central core structure called a medulla
-found on arms and legs
Terminal hairs = have central medulla
-hair bulb deep w/in the dermis or subcutis
-found on the scalp, groin, and axilla
Describe the hair cycle?
(a) Duration of each phase
(b) Total hairs, how many are shed each day?
Hair cycle: each hair undergoes an individual programmed cycle of growing and shedding
(a) growth (anagen- can last up to 5 years), cessation (catagen- around 2 weeks), and rest (telogen- around 3 months) until it falls off
(b) 100,000 total, 100 of which fall off each day
Distinguish the types of alopecia
Alopecia = hair loss
(a) areata = hair loss in patches
(b) totalis = hair loss on scalp
(c) universalis = hair loss on entire body
Histological finding of hair shaft in alopecia universalis
"swam of bees" = tons of lymphocytes attacking the hair follicle
-suggests autoimmune component => alopecia pts often have concomitant AI
What is a tricofolliculoma?
Benign adnexal tumor (benign tumor of the pilosebaceous unit)
-see 4-5 hairs (instead of just one) w/ a single orifice
(a) Clinically: see horses tail
(b) Usually punch biopsied out for cosmetic reasons
Describe the hair changes seen in hirsutism
(a) Common cause
Hirsutism = vellus hairs converted to terminal hairs
(a) Endocrine abnormalities, such as high T
What is androgenetic alopecia?
= male-patterned hair loss = hair loss due to hair follicle shrinkage under the influence of androgenic hormones
-terminal hairs converted to vellus hairs, shorter thinner hair w/ bulb in the superficial (instead of deep) dermis
Sebaceous, Eccrine, and Apocrine glands
(b) type of secretion
(a) Diffuse except for palms and soles
(b) Holocrine secretion
(a) Diffuse, especially on hands and soles
(b) Merocrine secretion- by exocytosis
(a) Limited to axilla and groin
(b) Secretion by decapitation- snout pinches off