Skin Pathology Flashcards
Characteristics of Vitiligo
Irregular, completely depigmented skin patches
Characteristics of Melasma
Irregular blotchy patches of hyperpigmentation on the face .
It is associated with sun exposure, oral contraceptive use and pregnancy
Characteristics of Freckles
Light brown macules on the face, shoulders and chest.
They are common in fair-skinned children and tend to darken and fade with the seasons due to sunlight exposure
Microscopically, freckles are characterized by increased melanin deposition in the basal cell layer of the epidermis with a normal number of melanocytes
Characteristics of Benign lentigo
Localized proliferation of melanocytes which cause small, oval, light brown macules
Microscopically, benign lentigos show linear melanocyte hyperplasia
Characteristics of Congenital nevi (birthmark)
Present at birth; giant congenital nevi have increased risk of developing ,melanoma
Characteristics of Nevocellular nevus (mole)
Benign tumor of melanocytes that is releated to sun exposure
Types of nevi include junctional compound and intradermal.
Nevi have uniform tan to brown color with sharp well-circumscribed borders and tend to be stable in shape and size
Characteristics of Dysplastic nevi (mole)
Larger and more irregular than common nevi and they may have pigment variation
Dysplastic nevus syndrome is autosomal dominant (CMM1 locus on chromosome 1) patients often have multiple dysplastic nevi
There is an increased risk of developing melanoma
Characteristics of Malignant melanoma
Malignancy of melanocytes whose incidence is increasing at a rapid rate with peak in ages 40-70
Risk factors include chronic sun exposure, sunburn, fair skin, dysplastic nevi syndrome, and familial melanoma
Melanomas characteristically form skin lesions of large diameter with asymmetric and irregular borders and variegated color
What causes malignant melanoma?
Loss of function mutation of the p16 tumor supressor gene
CDKN2A on chromosome 9
Somatic mutations of NRAS and BRAF
Characteristics of lentigo melanoma
Usually located on the face or neck of older individuals and has the best prognosis
Characteristics of superficial spreading melanoma
Most common type of melanoma and has a primarily horizontal growth pattern
Characteristics of acral lentiginous melanoma
Most common melanoma in dark-skinned individuals, it affects palms, soles and subungual area
Characteristics of nodular melanoma
Nodular tumor with a vertical growth pattern that has the worst prognosis of the melanoma
How is the prognosis of melanomas determined?
Determined by TNM staging
T status is based on the depth of invasion (Breslow thickness measured histologically in millimeters)
Characteristics of Acanthosis nigricans
Thickened, hyperpigmented skin of posterior neck, axillae, and groin
It is often associated with obesity and hyperinsulinism
On rare occasions it is associated with internal malignancy (stomach and other GI malignancies)
Characteristics of Seborrheic keratoses
Benign squamoproliferative neoplasms that are very common in middle-aged and elderly individuals
They may occur on the trunk, head, neck and the extremities
The lesions are tan to brown coin-shaped plaques that have a granular surface with a “stuck on” appearance
Characterized microscopically by basaloid epidermal hyperplasia and “horn cysts”
What is the sign of Leser-Trelat?
Associated with seborrheic keratoses
It is a paraneoplastic syndrome with the sudden development of multiple lesions which may accompany internal malignancy
Characteristics of Psoriasis
Autoimmune disorder with a clear genetic component that causes increased proliferation and turnover of epidermal keratinocytes
Common sites of involvement include the knees, elbows, and scalp; the classic skin lesion is a well demarcated erythematous plague with a silvery scale.
Removal of scale results in pinpoint bleeding (Auspitz sign)
Nail beds show pitting and discoloration
Common form is psoriasis vulgaris
Characteristics of pemphigus
Rare, potentially fatal autoimmune disorder that is characterized by intraepidermal blister formation
Autoantibodies directed against desmoglein 3 in keratinocyte desmosome, with resulting loss of intercellular adhesion (acantholysis) and blister formation
Microscopic examination shows intaepidermal acantholysis which leaves behind a basal layer of keratinocytes, which has a tombstone-like arrangment
Immunofluorence shows a net-like pattern of IgG staining between the epidermal keratinocytes that cause bullae
Characteristics of Bullous pemphigoid
Relatively common autoimmune disorder of older individuals characterized by subepidermal blister formation with tense bullae that do no rupture easily
The condition results from production of autoantibodies directed against keratinocyte hemidesmosome called bullous pemphigoid antigens 1 and 2
Immunoflorence shows linear deposits of IgG at the dermal-epidermal junction
Characteristics of Dermatitis herpetiformis
Rare immune disorder that is often associated with celiac sprue
Characterized by epidermal blister formation with itchy, grouped vesicles and occasional bullae on the extensor surfaces.
Production of IgA antibodies directed against gliadin and other antigens deposit in the tips of the dermal papillae and result in subepidermal blister formation
Immunoflorence shows granular IgA deposits at the tips of the dermal papillae
Characteristics of Porphyria cutanea tarda
Acquired and familial disorder of heme synthesis
Patients experience upper extremity blistering secondary to sun exposure and minor trauma
Microscopically, there are subepidermal blisters with minimal inflammation
Direct immunoflorences shows deposition of immunoglobulins and complement at the epidermal basement membrane and around dermal vessels
Characteristics of ichtyosis vulgaris
Common inherited (AD) skin disorder characterized by a thickened stratum corneum with absent stratum granulosum onset is in childhood.
Patients have hyperkeratotic, dry skin on the trunk and extensor surfaces of limb areas
Characteristics of xerosis
Common cause of pruritus and dry skin in the elderly that is due to decreased skin lipids
Cancer patients receiving epidermal growth factor receptor inhibitor are susceptible
Treatment is with emollients
Characteristics of eczema
Group of inflammatory skin diseases characterized by pruritius and epidermal spongiosis (edema)
Characteristics of acute eczema
Vesicular and erythematous rash
Characteristics of chronic eczema
Develops following repetitive scratching and is characterized by dry, thickened, hyperkeratotic skin
Characteristics of atopic dermatitis
Defects in the keratinocyte barrier are due to mutations in the filaggrin gene (FLG)
Characteristics of contact dermatitis
Either allergic type or photodermatitis type
Characteristics of polymorphous light eruption
Most common idiopathic form of photocermatosis and causes pruritic erythematous macules, papules, plaques or vesicles on exposure to sunlight
There is dermal edema and inflammation
Characteristics of verrucas (warts)
Caused by human papillomavirus.
Verruca vulgaris is the most common type
Characteristics of cutaneous lupus erythematosus
May be acute (facial butterfly rash), subacute (photosensitive rash on anterior chest, upper back, and upper extremities), or chronic (discoid plagues, usually above the neck)
Characteristics of erythema multiforme
Hypersensitivity skin reaction to infections or drugs.
Characterized by vesicles, bullar, and “targetoid” erythematous lesions.
Characteristics of Stevens-Johnson syndrome
Severe form of erythema multiforme.
Has extensive involvement of skin and mucous membranes
Characteristics of pityriasis rosea
Pruritic rash that starts with an oval-shaped “herald patch” and progresses to a papular eruption of the trunk to produce a “Christmas tree” distribution
It is clinically diagnosed, self-limiting and possibly a viral exanthem
Characteristics of granuloma annulare
Chronic inflammatory disorder that causes papules and plaques.
Palisaded granulomas are present microscopically
Characteristics of erythema nodosum
Raised, erythematous, painful nodules of subcutaneous adipose tissue, typically on the anterior shins, which can be associated with granulomatous disease and streptococcal infection
Characteristics of epidermoid cyst
Common benign skin cyst lined with stratified squamous epithelium and filled with keratin debris
Characteristics of actinic keratosis
Sun-induced dysplasia of the keratinocytes that causes rough, red papules on the face, arms and hands
Characteristics of squamous cell carcinoma (SCC)
Peak incidence at age 60.
Risk factors include chronic sun exposure (UVB), fair complexion, chronic skin ulcers or sinus tracts, long-term exposure to hydrocarbons, arsenic, burns, and radiation; immunosupression and xeroderma pigmentosum
Actinic keratosis and Bowen disease are precursors
Occurs on sun-exposed areas and causes a tan nodular mass which commonly ulcerates
Microscopic examination shows nest of atypical keratinocytes that invade dermis, often times formation of keratin pearls, and intracellular bridges (desmosomes) between tumor cells
What are the common mutations that cause SCC?
TP53 and HRAS
Characteristics of keratoacanthoma
Well differentiated squamous cell carcinoma which grows rapidly, dome-shaped nodules with a central keratinofilled crater; these are often self-limited and may regress spontaneously
Characteristics of basal cell carcinoma (BCC)
Most common tumor in adults in the western world; it is most common in middle-aged or elderly individuals and arises from the basal cells of hair follicles
Risk factors include chronic sun exposure, fair complexion, immunosuppression and xeroderma pigmentosum
Occurs on sun exposed, hair bearing areas (face), may form pearly papules; nodules with heaped-up, translucent borders, telangiectasia, or ulcers (rodent ulcer)
Microscopically shows invasive nests of basaloid cells with a palisading growth pattern
