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Chapter 2: Morphology and Terminology of Skin Lesions

Carol Soutor

INTRODUCTION TO CHAPTER

Identification and classification of a patient's skin lesions are important steps in the diagnosis of any skin disorder. The numerous descriptive terms used in dermatology can be overwhelming and at times confusing as there are some variations in the use and meaning of these words in the literature.1 However, a few simple terms can be used to describe the cutaneous findings in most skin diseases. Using proper terminology to describe skin findings is essential for both documentation and communication with other clinicians. The effort to use precise descriptive terms also encourages a clinician to look with more care and more closely at a patient's skin lesions. The key features of skin lesions are (1) the type of lesion, (2) secondary changes to the surface of the lesion, (3) the color of the lesion, (4) the shape of the lesion, and (5) the arrangement and distribution of the lesions.

TYPES OF LESIONS

The first step is categorization of the primary skin lesion(s). This may be difficult if the lesions are excoriated or if the examination takes place late in the disease process. The lesion may need to be lightly touched or deeply palpated to accurately assess its features. Table 2-1 lists the 10 most common morphological terms for types of skin lesions. These are based on:

  • Diameter of the lesion.

  • Relationship of the lesion to the surface of the skin—is the lesion flat or elevated above the surface of the skin?

  • Composition of the lesion—is it fluid filled or solid?

Table 2-1.Primary lesions and their morphology.
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Table 2-1. Primary lesions and their morphology.
Terminology Diameter Morphology Example

Macule

Patch

<0.5 cm

>0.5 cm

 Flat, level with surface of skin Tinea versicolor (Figure 2-1)

Papule

Plaque

<0.5 cm

>0.5 cm

 Solid, elevated lesion Dermatitis (Figure 2-2)
Wheal Any size White to pink edematous papule or plaque that lasts less than 24 h Urticaria (Figure 2-3)
Nodule >0.5 cm Dermal or subcutaneous solid, elevated lesion Amelanotic melanoma (Figure 2-4)

Vesicle

Bulla

<0.5 cm

>0.5 cm

 Blister containing fluid or blood Pemphigus vulgaris (Figure 2-5)
Pustule <0.5 cm Cavity filled with pus, may be sterile Pustular psoriasis (Figure 2-6)
Cyst >0.5 cm Cavity filled with pus or keratin Epidermal cyst (Figure 2-7)
Figure 2-1.

Macules and patches. Tinea versicolor.

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Figure 2-2.

Papules and a plaque. Contact dermatitis due to nickel in metal button in a child with atopic dermatitis.

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Figure 2-3.

Wheal. Urticaria.

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Figure 2-4.

Nodule. Nodular amelanotic melanoma.

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