This document summarizes several pre-malignant and malignant epidermal tumors and acute inflammatory dermatoses. It describes actinic keratosis as a premalignant skin lesion caused by UV damage that can progress to squamous cell carcinoma. Squamous cell carcinoma is described as arising from UV damage or other causes and often presents as an ulcer. Basal cell carcinoma is summarized as the most common skin cancer, locally aggressive but non-metastatic, appearing on sun-exposed skin. Urticaria, eczema, and erythema multiforme represent acute inflammatory dermatoses and their histological features are outlined.

1. Pre malignant and malignant
epidermal tumours

2. Actinic Keratosis (Solar keratosis)
• Premalignant skin lesion induced by ultraviolet light
damage
– Sun exposed areas (face, hands, forearms)
– Excess production of keratin to produce cutaneous horns
– May progress to squamous carcinoma in situ (Bowen’s disease)
or invasive cancer
– Lesion measures <1cm, tan brown, with rough sand paper like
consistency
– HISTOLOGY:
– - Parakeratosis and atypia (dysplasia) of the keratinocytes
– Solar damage to underlying elastic and collagen tissue (solar
elastosis)

3. Actinic keratosis – note scaling appearance

4. ACTINIC KERATOSIS
• Note the epidermal atypia and the parakeratosis

5. Squamous Cell Carcinoma
• Occur secondary to:
– Ultraviolet light damage
– Industrial carcinogens
– Chronic ulcers or sinus tracts (particularly chronic
osteomyelitis), Burn scars (Marjolin’s ulcer)
– Chewing tobacco (inside mouth) -Leukoplakia
– Radiation
– Patients who are immunocompromised
– Xeroderma pigmentosum
– Viral infections –HPV type36

6. Squamous Cell Carcinoma
• Gross: Shallow ulcer with a raised edge
• Microscopic: Usually well-differentiated tumor
with invasion of the dermis
• They exhibit variable differentiation ranging from
polygonal cells with keratinization and
intercellular bridges to highly anaplastic round
cells with scant keratinization
• Unlike BCCs, SCCs may develop on both sun-
exposed and non exposed areas of the body (the
latter are more likely to metastasize)

7. Squamous Cell Carcinoma of Lip in
Pipe Smoker

8. SCC

9. SCC – Keratin pearl

10. Basal Cell Carcinoma (BCC)
• Most common malignant tumor of the skin
• Occurs on sun-exposed, hair-bearing surfaces
• BCC’s are locally aggressive, infiltrating
cancers arising from the basal cell layer of the
epidermis
• Infiltrate the underlying superficial dermis
• DO NOT METASTASIZE
• Commonly located on the face on the inner aspect of
the nose, around the orbit and the upper lip

11. Basal Cell Carcinoma
• Appear as raised nodules containing a central crater
with a pearly-colored skin surface and vascular
channels (“pearly-white lesion”)
• Histology: Proliferation of basaloid cells arising from
the epidermis and extending into the dermis in lobules
or strands. Tumour cells also exhibit peripheral
pallisading. Clefts separating tumor cell nests from the
dermis are typical.
• Basal cell nevus syndrome: AD inheritance with
multiple BCC of skin & many other tumours in bone,
CNS, reproductive organs

12. Basal Cell Carcinoma
• Note the rolled pearly border & Prominent blood
vessel

13. Basal Cell Carcinoma
• Locally aggressive – Rodent ulcer

14. Basal Cell Carcinoma
• Typical clefting is noted

15. Basal Cell Carcinoma
• At higher power note the peripheral
pallisading of cells

16. Acute inflammatory dermatoses
• Urticaria
• Eczema
• Erythema multiforme

17. Urticaria
• Urticaria (hives) refers to the presence of
edema within the dermis and itchy
elevations of the skin
• Angioedema refers to edema in the
subcutaneous tissue

18. URTICARIA - pathophysiology
• Type I hypersensitivity
• Antigen stimulated, IgE mediated release of mast cell
granules
• Follows exposure to pollens, foods, drugs, pressure,
temperature or other stimulus
• C1 esterase inhibitor deficiency causes uncontrolled
complement activation (hereditary angioneurotic
edema)

20. Urticaria
Histology: Dermal edema and a minimal perivascular infiltrate of lymphocytes,
eosinophils and neutrophils. These changes may be relatively inconspicuous
and often very little is seen in the biopsy

21. Acute Eczematous dermatitis
• It is a clinical term embracing many
pathologically different lesions
• Eczema means “to boil over”.
• These lesions initially are characterized by red,
papulovesicular (Vesicles and bullae), oozing
crusted lesions (Bacterial superinfection) and
later with persistance forms raised scaling
plaques (Hyperkeratosis and acanthosis).

22. Stages of Eczema Development
A: Initial dermal edema and perivascular infiltration by inflammatory cells is followed
within 24 to 48 hours by epidermal spongiosis and microvesicle formation (B).
C: Abnormal scale, including parakeratosis, follows, along with progressive epidermal
hyperplasia (D) and hyperkeratosis (E) as the lesion enters into a more chronic stage.

23. Acute Eczema

24. Contact (Spongiotic) Dermatitis
• Histology: Acute phase - spongiosis, migration of
lymphocytes into the epidermis;

25. Eczematous (Spongiotic) Dermatitis
Note numerous spaces in the epidermis. This corresponds to vesicles seen clinically
and is typical for spongiotic dermatitis. Contact dermatitis is the major sub-category
of Eczematous dermatitis

26. Classification of Eczematous
Dermatitis
• Atopic Dermatitis
• Allergic Contact Dermatitis
• Drug-related eczematous dermatitis
• Photoeczematous eruption
• Primary Irritant dermatitis

27. Allergic Contact Dermatitis

28. Irritant Contact Dermatitis
• Due to the local toxic effect of the chemical on
the skin (e.g. detergents present in soaps,
shampoos, household cleaners)

29. Photodermatitis in patient taking
tetracycline
• Similar to allergic
contact dermatitis
except the reaction is
dependent on
ultraviolet light
• Drugs that are
photosensitizing
include:
– Tetracycline
– Sulfonamides
– Thiazides

30. Erythema Multiforme
• Hypersensitivity reaction to an infection, drugs,
various autoimmune diseases, or pregnancy
– Probable immunologic disease
– Infection associations include:
• Mycoplasma
• HSV I and II (MOST COMMON Herpes simplex)
– Drug associations include:
• Sulfonamides
• Anticonvulsants - Phenytoin
• Penicillins
• NSAIDS

31. Erythema multiforme
• EM Minor - Erythematous macules, papules, or
vesicles
– Papular lesions frequently look like a target with a
pale central area
– Commonly located on the palms and soles
• EM major – (Stevens-Johnson syndrome)-Extensive
skin and mucous membrane involvement with fever
and respiratory symptoms
• Histology – Cytotoxic reaction where there is
degenerating keratinocytes. Early lesions have
lymphocytic infiltrate in the dermo-epidermal
junction but later zones of epidermal necrosis occurs
forming blisters

32. Erythema Multiforme

33. Erythema Multiforme
Note ‘target-like’ papules

34. Target Lesions in Erythema Multiforme

35. Erythema Multiforme
• Note the interface change, necrosis of skin, and
lifting of necrotic epidermis. This corresponds to
the center of the target lesion.

36. Erythema Multiforme
• Early lesion or periphery of target lesion. Note
milder changes, basal layer focally obscured by
inflammation