Skin Histopathology

8/12/10 8 AM
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What 4 things must be done before turning on the microscope?
Tissue processingH&E stainSpecial stainsImmunohistochemistry
What is tissue processing?
Skin biopsy, fix tissue in formalyn
What is H&E stain?
Standard stain for all tissues- stains the nuclei purple (hematoxylin) and the cytoplasm pink (eosin)
What is immunohistochemistry?
Selecting for certain proteins in tissue sample. Use antibody to bind to a certain antigen in a tissue.
What are the 4 primary cells of the epidermis?
KeratinocytesMelanocytesLangerhans cellsMerkel cells
What are the 3 primary components of the dermis?
FibroblastsDermal fibers (collagen, elastin)Ground substance
What are the adnexae?
Hair folliclesSebaceous glandsSweat glands
Skin pathology is divided into what 2 types of disorders?
1. Non-neoplastic (inflammatory, infectious, immunologic)2. Neoplastic
How is a skin disorder diagnosed?
By pattern recognition
What are the microscopic patterns in the epidermis?
1. Hyperkeratosis (orthohyperkeratosis, parahyperkeratosis)2. Hyper/hypogranulosis3. Acanthosis (psoriasiform, regular; psoriasiform, irregular; papillomatous; pseduoepitheliomatous)4. Atrophy5. Spongiosis6. Vacuolar-interface alteration7. Dyskeratosis8. Blistering pattern (subepidermal, intraepidermal, acantholysis)
What is parakeratosis?
Hyperplasia + visible nuclei in the stratum corneum
What is an example of a skin disorder with orthohyperkeratosis?
Lichen planus
What is an example of a skin disorder with parakeratosis?
What is hypergranulosis?
Hyperplasia of the stratum granulosum
What is hypogranulosis?
Hypoplasia of the stratum granulosum
As a rule of thumb, which of these goes together?
Orthohyperkeratosis - hypergranulosisParakeratosis - hypogranulosis
What are the 4 microscopic patterns in the dermis?
1. Dermal infiltrates (superficial perivascular, superficial and deep, lichenoid, diffuse infiltrates)2. Dermal fiber alterations3. Intercellular matrix alterations4. Vascular alterations
What is the microscopic pattern in the subcutis?
Inflammation of subcutis = panniculitisseptal infalmmationlobular inflammation
What are the 2 types of alterations in skin pigmentation?
1. Hyperpigmentation2. Hypopigmentation
Histiocytes accumulate in superficial dermiscommon after dermatitis
Lack of melanocytes and pigmentationcommon in vitiligo
Name the 3 spongiotic dermatoses
1. Contact dermatitis2. Nummular dermatitis3. Autosensitization reaction
Name the 2 vacuolar interface dermatoses
1. Lichenoid infiltrate (lichen planus)2. Without lichenoid infiltrate (lupus, erythema multiforme, drug eruptions)
Name the 3 psoriasiform dermatoses
PsoriasisPityriasis rubraLichen simplex chronicus
Intraepidermal blisters are called ________
Subepidermal blisters are called ____
What is a neoplasm?
Abnormal growth of a tissue that continues even after the stimulus is gone.
What is seborrheic keratosis?
Benign neoplasm of the keratinocytes
What are the intermediate neoplasms of keratinocytes?
Actinic keratosisSquamous cell carcinoma in situ
What are the malignant neoplasms of keratinocytes?
Invasive SCCBCC
What is seborrheic keratosis?
Benign growthClinically - tan to dark brown, smooth, round lesion; stuck-on appearanceHistologically - uniform basaloid cells and pseudo-horn cysts, acanthosis (epidermal hyperplasia of stratum spinosum), sharply demarcated from adjacent epidermis
What is actinic keratosis?
Preneoplastic lesion caused by sun exposureatypical keratinocytes in the lower part of the epidermisParakeratosis + hypogranulosisParakeratosis usu spares the areas above the folliclessolar elastosis
(Recall: parakeratosis = hyperplasia of the stratum corneum with preservation of nuclei. Usually accompanies hypogranulosis or loss of granular layer)
What is solar elastosis?
Bluish changes seen in epidermis due to sun damage
What is squamous cell carcinoma?
The 2nd most common tumor (BCC > SCC > melanoma)Caused by = sun exposure, carcinogens, burn tissue, immunosuppressionClinically = sharply demarcated red lesions (in situ); ulcerated, nodular lesions (invasive)

What is the histologic appearance of SCC in situ?
Atypical keratinocytes that span the full thickness of the epidermis, but do not go into the dermis
What is the histologic appearance of SCC invasive?
Nests of atypical keratinocytes invading the dermiseosinophilic cytoplasm and large, vesicular nucleikeratin formation (bc stratum corneum will be formed from the atypical keratinocytes)
what is basal cell carcinoma?
Most common skin cancerMalignant, slow-growing tumor that does NOT metastasize
What is the clinical appearance of BCC?
Pearly, telangiectatic noduleRodent ulcer
What is the histologic appearance of BCC?
Basaloid (bluish) cells in nodules, does not invade the dermis, surrounding by peripheral palisading
What is a dermatofibroma?
Benign tumor of the fibroblast (main cell of the dermis)
What is the clinical apperance of a dermatofibroma?
Tan to brown firm papules
What is the histologic appearance of a dermatofibroma?
Fibroblasts, foamy histiocytes, and overlying epidermal hyperplasia
What is a dermatofibrosarcoma protuberans?
A well-differentiated fibrosarcoma of the skin that rarely metastasizes but is locally aggressiveFirm solid nodulesHIstologically - whorls and cartwheels of fibroblasts

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