Basic Skin Path
I. Basic Histo:
v “Barry Sanders Goes Long Constantly”
v Skin = Mostly Keratinocytes
II. Path Findings Not Unique to the Skin
A. H & E: Tumors = Blue (basophilic nuclear staining),
W More malig = more blue
W Pink = usually benign
B. Granulomas
W Enlarged Macs -> Epithelioid Cells -> Fuse -> Multinucl Giant Cells
W DDx:
1. Infectious: mycobacterial[caseating] (leprosy [linear: follow peripheral nerves], Tb, atypical), syphilis, deep fungal, etc.
v Usually accomp by neutrophils or plasma cells
2. Foreign body: keratinous material (from ruptured cysts or follicles), splinters, sutures, etc.
3. Sarcoidosis [non-caseating]
W Stains:
1. Ziehl-Neelson & Fite for AFB
2. PAS & GMS (Gomori Methenamine Silver) for fungi
C. Granulation Tissue: prolif. blood vessels, fibroblasts, & inflam. cells
v “proud flesh”
v usually @ base of ulcers
D. Fibrosis: “scar” (aka cicatrix), increase of collagen & fibroblasts (later stage than granulation)
E. Ulceration: full thickness loss of epithelium
v crust = fibrin & neutrophils
v base = granulation & fibrosis
F. Vasculitis: destruction & necrosis of vessel walls w/ accum of inflamm cells & fibrin w/i the wall
v RBC’s extravasate -> PURPURA
v “Nuclear dust”: Neutrophilic nuclei scattered thru the dermis
v Most commonly PALPABLE PURPURA of lower legs
G. Tumor Cell Types
v Carcinomas = epithelial cells
v Sarcomas = fibroblasts, muscle, peripheral neural elements, endothelial cells lining vessels (“anything that is not epithelial, except lymphoma/leukemia”)
1. Spindle Cell Tumors: elongated, spindle-shaped nuclei, usually sarcomas
2. Epithelioid Cell Tumors: large cells w/ abundant pink cytoplasm & pale “vesicular” nuclei.
v Epithelial Tumors (Squamous Cell CA) & Melanomas
3. Basaloid Cell Tumors: small cells w/ hyperchromatic nuclei, & little cytoplasm
v Basal Cell Carcinoma
III. Path Changes in the Skin
A. Neoplasms: most arise in epidermis/invade dermis
1. Most arise from Keratinocytes
a. Basal Cell Carcinoma (immature keratinocytes)
b. Squamous CC
c. Seborrheic keratosis
d. Actinic keratosis
2. Melanocytes
a. Malig Melanoma
b. Benign Melanocytic Nevi
3. Mesenchymal
a. Dermatofibroma: mostly fibroblasts & macs
b. Neurofibroma: benign tumor of Schwann cells & axons
c. Neurofibrosarcoma: aka Malignant Schwannoma
d. Leiomyoma
e. Leiomyosarcoma
f. Hemangioma: vascular endothelial cells, benign
g. Angiosarcoma: malignant endothelial cells
4. Metastic to the Skin
v Usually from breast, lung, or colon
v Usually found in scalp or trunk skin
B. Dermatitis
1. Inflammatory Cell Types
a. Neutrophils = “segmented” = Acute
v Pustules, folliculitis, vasculitis, cellulites, ulcer surface
b. Lymphocytes & Macs = “mononuclear” = chronic
v Lymphocytes are in most skin diseases
v Predominantly Macs = granuloma
c. Plasma Cells: IgA production in Mucous Membranes
v Syphilis & Multiple Myeloma
d. Eos: “allergic” Type I Hypersensitivity (eg Urticaria)
v Arthropod bites, Drug Rx, Atopic dermatitis
e. Mast Cells: Normal skin or Mastocytosis
2. Inflammatory Patterns of Dermatitis
a. Perivascular: around dermal vessels
b. Lichenoid: dermal band of infl. cells just below epiderm.
c. Diffuse
d. Nodular: large aggregates of infl. cells
e. Folliculitis (“Pimples”): around hair follicles or sebaceous gl.
f. Panniculitis: subcutaneous fat
3. Edema: pale staining dermis
v Hives = Urticaria = wheals
v Spongiosis = betwn keratinocytes in epiderm.
o Seen in Eczemas
4. Epidermal Changes
v Normally no nuclei in S. Corneum
v Parakeratosis = nuclei in S. Corneum, pathological
o Scales = manifestation of epidermal problems
o Epithelial hyperplasia = many chronic skin diseases
5. Hyperplasia = # of normal cells in normal arrangement, may regress
v Neoplasia = # of abnormal cells w/o much chance of regression
v Hyperkeratosis = hyperplasia of S. Corneum (callous, wart, psoriasis)
v Acanthosis: thick spinous (Malphigian) layer
o Mostly prickle cells
o Prickle cells: keratinocytes (acanthocytes) with desmosomal “prickles”
o Typically occurs with hyperkeratosis
6. Dermal Changes
v Solar elastosis: degenerative dermis due to sun damage
o Dermal connective tissue stains smudgy basophilic instead of the normal pink
o Elastic fibers = clumped & dysfunctional -> wrinkles
Tags: Actinic keratosis, Basal Cell Carcinoma, Basaloid Cell Tumors, basophilic nuclear staining, Dermatofibroma, fibroblasts, granulomas, leprosy, Sarcoidosis, Seborrheic keratosis, Spindle Cell Tumors, syphilis, vasculitis, Ziehl-Neelson & Fite
