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“You see, but you do not observe”

—Holmes to Watson in “Scandal in Bohemia,” by Arthur Conan Doyle, 1892

Skin Lesions and Diagnosis at a Glance
  • A patient and thorough approach to the evaluation decreases the risk of making an incorrect diagnosis or overlooking another diagnosis.
  • Knowledge and appropriate use of dermatological terminology are fundamental.
  • Recognition of disease patterns requires repeated patient encounters.
  • The history is indispensable in elucidating complex diagnoses.
  • The entire mucocutaneous surface, as well as the hair and nails, should be examined whenever reasonable.
  • Morphologic characteristics derived from cell type in skin must be carefully scrutinized.
  • Diseases have characteristic morphology and distribution.
  • Common pitfalls in dermatologic diagnosis exist and can be avoided.

The diagnosis and treatment of diseases that affect the skin rest on the physician's ability to use the language of dermatology, to recognize the primary and sequential lesions of the skin, and to recognize the various patterns in which they occur. In this chapter, we discuss a fundamental approach to the patient presenting with a skin problem. We introduce the technical vocabulary of dermatologic description, the “dermatology lexicon.” It is important to know and use this standard terminology, as it is the first step in generating a differential diagnosis. Once a lesion has been described as a pearly, flesh-colored, telangiectatic, ulcerated nodule, the experienced physician puts basal cell carcinoma at the top of the differential diagnosis. It is also important to use standard dermatologic terminology for consistency in clinical documentation, in research, and in communication with other physicians.

The process of examining and describing skin lesions may be likened to that of viewing a painting. First, one stands back and takes in the whole “canvas,” viewing the patient from a few feet away, at which distance an overall assessment of the patient's general and cutaneous health may be made. One may note such findings as skin color and turgor, presence of pallor or jaundice, degree of sun damage, and the overall number and location of lesions. Next, one looks more closely at the “trees” or “mountains” that make up the landscape, describing and categorizing the specific lesions on the patient. Finally, one may closely examine the details of the canvas, taking in the texture and brush-strokes, using magnification to see the borders of a nevus or compressing a lesion to see if it blanches. Just as a knowledgeable viewer of art may recognize a work of Georges Seurat by its tiny, dot-like brush strokes, an experienced observer of the skin can recognize a melanoma by its asymmetry, irregular borders, and multiple colors.


Dermatology is a visual specialty and some skin lesions may be diagnosed at a glance. Nonetheless, the history is important and in complex cases, such as the patient with rash and fever or the patient with generalized pruritus, history may be crucial. Dermatologists vary ...

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