Oral Medicine and pathology

1. Nomenclature: Basic
Lesional Morphology

2. Introduction
• Few basic principles – critical in understanding
the interpretation of physical signs
• These principles arise from the morphological &
functional diff of the 3 main levels of the skin
Epidermis
Dermis
S/C fat

3. Epidermis
 Outer cellular layer of the skin – keratinocytes diff to form a dead
layer of scale – stratum corneum
 Any disorder – with altered scaling – must involve some epidermal
pathology or changes in epidermal function
 Melanocytes – basal layer
 Langerhans cells- Immunological function
 Melanocytes – can drop into dermis – following inflammation
 Color – varies from reddish brown to blue black – depending on
the shape, clustering number & depth of pigment granules

4.  Disorders of the brown pigment – due to abnormalities
of the melanocytes
 But can also occur – becoz loss of melanin pigment
from the epidermis & accumulate in dermis after
inflammation

5. Dermis
 Dermis – fibrous part of the skin
 Imp complex structure in may blistering disorders
 Specialized epidermal structures –
 Hair follicles
 Sweat ducts
 Also contains blood supply – skin
 Nutrients diffuse into epidermis – no direct blood supply
 Cells of immune system – must pass into the dermis from bv –
even if the site of inflammatory stimulus is epidermis

6. Imp diagnostic points –
 Any disorder with altered scaling - involve some epidermal pathology
 Disorders of the brown pigment - related to the melanocytes of the
basal epidermis
 Abnormalities of the blood vessels & the origin the free blood in the
skin, must be within the dermis
 Lesions in the fat layer may be diff to see or feel as the fibrous dermis
acts a barrier

7. Discrete flat lesion, not raised above the adjacent
normal skin
Large macule – patch
Size limit at which a macule becomes a patch
varies in diff texts – 1.5-2cms
Usually darker red or brown than normal skin,
Fine scale – feature of macule – include altered
keratinocyte function & change in color
Slightly depressed macules – atrophic macules
Epidermal macule – lentigo – localised increase
in no of basal melanocytes
Dermal macule – purpura – due to extravasation
of blood from capillary vessels without epidermal
change

8. Papules & nodules –
Discrete lesions – usually visibly raised above the skin
surface
Typical of some common tumors –
Basal cell carcinoma
Melanocytic naevi
Nodules – may also lie deep to the dermis – lipoma
Size at which the a papule should be called a nodule –
varies 5-10mm
All nodules starts as papules but not all papules will grow
into nodules
Useful to record – Actual size, duration, apparent changes
in size & surface of the lesion

9. Plaques –
Raised lesion with a flat top
Scaling frequently present
E.G – lesions of psoriasis

10. Weals –
Transient swelling of the skin due to dermal fluid
Often referred to as blisters – but here the fluid is dispersed unlike
blisters
Specific features –
• short course of individual lesions – min to
hrs – leaving little or no residual abnormality
• dermal swelling – sharp defined borders
•No epidermal component
•Red color – vasodilation

11. Vesicles & bullae –
Both terms – describe diff sizes of blister
Discrete accumulation of fluid – components run out when top is incised
Occur within or just below the epidermis
Vesicle is small & blister is large – cut off –
5-10mm
Useful to note the size range

12. Pustules –
Epidermal or upper dermal accumulation of pus – breakdown product of PMNL
Clinically – yellow or green
Deeper collection of pus –abscess – but the
content not visible through the skin
Some pustules – infiltration of PMNL
few – start as vesicle & gradually accumulat
pus cells

13. Ulcer, erosion, excoriation & fissure
Ulcer, erosion, excoriation & fissure – are all breaks in
the integrity of the skin surface
An erosion – superficial, involving the epidermis only
An ulcer – extends into the dermis
A fissure – small, deep, but narrow ulcer with a slit or
cleft shape – angular chelitis
An excoriation – can form either an erosion or an ulcer
& implies that the cause of the lesion is external

14. Scale & crust
Terms often confused – becoz they occur together
Scale – flake at the skin surface which
contains an accumulation of keratinized
epidermal cells – icthyosis
Denotes – abnormality in st corneum formn
Hyperkeratosis – thickened st corneum –
distinguished from scaling – Keratoacanthoma
Crust – dried exudate of blood or serous fluid
on the surface of the lesions - scab - impetigo
Crusting – occurs increased keratinisation
Sq cell ca

15. Atrophy –
Is loss of skin substance – producing thinning
May be epidermal, dermal or a combination
Dermal atrophy – after injury

16. Erythema, telangiectasia, purpura, petechiae & ecchymosis
Terms – describe vascular changes
Erythema – diffuse redness due to increased
Visibility of I/V blood – due to vasodilatation
Telangiectasia – individually visible dilated
vessels
Purpura – visible extravascular blood
If this occurs – tiny pinpoint spots – petechiae
Large area of extravasated blood – ecchymosis

17. Poikiloderma -
Combination of atrophy, pigmentation &
telangiectasia – several disorders –
Psoriasis