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It is important to have a shared common terminology for the description and diagnosis of skin disorders. While immediate pattern recognition may be available to those clinicians with the greatest experience and expertise, recognizing morphologic characteristics of skin disorders is a great first step to diagnosis. In these days of Google searches and excellent online dermatologic resources, being able to describe a lesion or rash may help clinicians arrive at an excellent differential diagnosis simply by putting the appropriate terms in a search engine. The terminology that we will define in this chapter includes morphology, pigmentation, shapes, other descriptors, and distribution.


Primary morphology are the terms we use to describe the initial changes of a skin lesion or eruption. Secondary morphology terms are based on what happens to lesions and eruptions over time. Although we present morphology terms divided into these two categories, the most important information is the terms themselves.

Primary morphology:

  • Macule—a nonpalpable, well-circumscribed change in skin color less than 1 cm

  • Patch—a nonpalpable, well-circumscribed change in skin color greater than 1 cm

  • Papule—a palpable, elevated, solid skin lesion less than 1 cm

  • Plaque—a palpable, elevated skin lesion greater than 1 cm

  • Wheal—a transient smooth papule or plaque seen in urticaria

  • Vesicle—a small fluid-containing blister less than 1 cm

  • Bulla—a large fluid-containing blister greater than 1 cm

  • Pustule—a vesicle containing pus

  • Nodule—a solid, nonsuperficial skin mass between 1 and 2 cm

  • Tumor—a solid skin mass greater than 2 cm

Secondary morphology:

  • Scale—flaking off of the stratum corneum

  • Crust—dried exudate

  • Excoriation—areas of skin damage that are linear and secondary to scratching or scraping

  • Lichenification—thickening of the skin with prominent skin lines secondary to repeated rubbing or scratching

  • Erosions—loss of areas of the epidermis secondary to manipulation of the skin or popping of blistered areas

  • Ulcers—deeper areas of skin loss that extend at least into the deeper dermis

  • Fissures—cracking of the skin in a somewhat linear pattern

  • Atrophy—thinning of the skin

  • Hypertrophy—thickening of the skin


Primary morphology

FIGURE 110-1

Macule—labial melanotic macule. (Reproduced with permission from Richard P. Usatine, MD.)

FIGURE 110-2

Patch—speckled nevus. (Reproduced with permission from Richard P. Usatine, MD.)

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