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A common lesion causes a great deal of worry

Joe R. Monroe, PA-C, MPAS

Joe Monroe works at the Regional Dermatology Clinic, Bartlesville, Oklahoma, and is the department editor for Dermatology Digest. He has indicated no relationships to disclose relating to the content of this article.

CASE

A 44-year-old woman presented to the dermatology clinic with a lesion on her leg. She did not know exactly how long it had been there. She said that most of the time, the lesion produced no symptoms, although occasionally it caused an “itchy, crawly” sensation. The patient was otherwise healthy, with no history of skin disease. She had little sun exposure history, and hence little sun damage. She denied any history of injury, foreign body, or insect bite in that area. No treatment of the lesion had ever been attempted. Her primary care provider had referred her to us somewhat reluctantly because he felt strongly that the lesion was benign. The patient remained unconvinced, however; a friend of hers had just received a diagnosis of melanoma.

On examination, a firm, reddish-brown, 1-cm nodule was noted on the patient’s calf (see Figure 1). The lesion was nontender and demonstrated a faint, targetoid, brown peripheral ring of pigment. No other significant lesions were noted on the patient’s skin.

THIS LESION IS MOST LIKELY A

Nevus
Dermatofibrosarcoma protuberans
Dermatofibroma
Melanoma

DISCUSSION

The lesion is almost certainly a dermatofibroma, which is an extremely common benign tumor of uncertain origin. A nevus, which is more commonly known as a mole, can manifest in a number of morphologic forms, depending on the type, but will seldom be seen on the calves. In addition, moles are almost never this firm. Dermatofibrosarcoma protuberans, a malignancy originating in the dermis, is fortunately rare and seldom takes on the look of this patient’s lesion. A melanoma can certainly be raised, but 80% are essentially macular and almost never firm to the touch.

Dermatofibromas are very common, and this case—the location of the lesion, the gender of the patient, and the morphology—is an archetypical example. Many dermatofibromas are not raised and instead are said to “dimple” when lateral digital pressure is exerted. However, about one-third of them are elevated above the skin and manifest as the lesion did in this case. It is common for dermatofibromas to tingle or itch periodically and to show up in multiples in adults. The darker the patient’s skin, the darker the pigment in the lesion will be, especially in the periphery.

Dermatofibromas develop most commonly on the extremities, typically the lower leg, and are said to result from an insect bite or other injury to the leg. Truth be known, however, there is no way to prove that assertion and there is reason in some cases to doubt it. In any case, these lesions have almost no malignant potential—although they often exemplify what patients imagine skin cancer to look like.

Treatment When dermatofibromas are removed (by surgical excision), the reason is almost always that the patient has sustained repeated injury from shaving or that the patient is worried. The histopathologic picture is usually quite pathognomonic, although these lesions do rarely show changes suggestive of malignancy.

In this case, the patient could not provide a firm history of how long the lesion had been present. For that and other reasons, the lesion was excised and sent to pathology, which confirmed the diagnosis. Large dermatofibromas, like this one, run deep, and excision requires cutting well into adipose tissue and then closing in two layers. Even with such closure, however, the resultant scar is often less than satisfactory—so it is best to leave these lesions alone, if possible. JAAPA