Basic Lesions in Dermatology

Macule

Macule is a change in skin color compared to the surrounding area, flat and may be well-defined or ill-defined.

• Diameter:

• < 1cm: Macule

• > 1cm: Patch

• Color: Depends on the amount of melanin accumulation

• Types of macule:

• Pigmented macule: Due to melanin, can be congenital or due to pigmentation.

• Melasma: Pigmented macule due to melanin.

• Non-melanin macule:

• Amalgam macule: For example, macule due to amalgam metal.

• Erythema: Due to vasodilation, disappears when pressed.

• Vascular macule: Due to vasodilation or flat hemangioma.

• Purpuric macule: Does not disappear when pressed (glass test).

Papule

• Papule: Firm, raised lesion on the skin surface, < 1cm in size, located in the epidermis or superficial dermis.

• Patch: Similar to papule but > 1cm in size.

• Nodule: Due to irritation (fibroma), lipoma, neuroma due to trauma.

• Tumor: Hard, protruding from the mucosa, extending deep.

• Verrucous lesion: Warts, squamous cell carcinoma, hyperkeratosis develops into an area of tissue with multiple papillae.

Vesicle

• Vesicle: Raised above the skin surface, well-defined, D <= 0.5 cm, contains clear fluid.

• Erosion, ulcer: Formed when the vesicle ruptures.

• Pustule: Vesicle containing pus inside due to infection.

• Bulla: Vesicle with a diameter of 6-8mm.

• Cyst: Wall is epithelium (buried or residual).

• Ulcer: Extends beyond the basement membrane, deep into the dermis.

• Erosion: Deep into the dermis, usually neat, in the form of lines, streaks, oozing blood, not through the basement membrane, secreting fluid, red in color.

• Scar: Formed to replace lost tissue due to injury or inflammation, left behind when healed.

Related diseases

• Vitiligo: The basic lesion is patch.

• Lichen planus: The basic lesion is papule.

• Macule: Often found in diseases like: viral infection, fungal infection, drug reaction, oral infection.

Erosion

• Characteristics:

• Loss of tissue beyond the basement membrane.

• Bottom has fibrous tissue, connective tissue, infiltration of neutrophils.

• Irregular or regular margins.

• May be painful.

Note: The above information is for reference only, it is necessary to be examined and diagnosed accurately by a dermatologist.