A 25-year-old woman reports a firm nodule on her leg that gets in the way of shaving her leg (Figure 160-1). Upon questioning, the nodule may have started there after she cut her leg shaving 1 year ago. She is worried it could be a cancer and wants it removed. Close observation showed a brown halo and a firm nodule that dimpled down when pinched. A diagnosis of a dermatofibroma (DF) was made and the choices for treatment were discussed.
Dermatofibroma on the leg of a 25-year-old woman that may have begun after she cut her leg shaving 1 year ago. Note the brown halo, pink hue, and raised center. (Courtesy of Richard P. Usatine, MD.)
DF is a benign fibrohistiocytic tumor, usually found in the mid dermis, composed of a mixture of fibroblastic and histiocytic cells. These scar-like nodules are most commonly found on the legs and arms of adults.
Also called benign fibrous histiocytoma.
- Occurs more often in women (male-to-female ratio is 1:4).1
- Found in patients of all races.
- Approximately 20% occur in patients younger than age 17 years.1 In one case series, 80% occurred in people between the ages of 20 and 49 years.2
- Uncertain etiology—Nodule may represent a fibrous reaction triggered by trauma, a viral infection, or insect bite; however, DFs show clonal proliferative growth seen in both neoplastic and inflammatory conditions.3
- Multiple DFs (i.e., >15 lesions) have been reported associated with systemic lupus erythematosus, HIV infection, Down syndrome, Graves disease, or leukemia, and may represent a worsening of immune function.1 A case of familial eruptive DFs has also been reported associated with atopic dermatitis.4
- Firm to hard nodule; skin is freely movable over the nodule, except for the area of dimpling.
- Color of the overlying skin ranges from flesh to gray, pink, red, blue, brown, or black (Figures 160-2 and 160-3), or a combination of hues (Figure 160-4).
- Dimples downward when compressed laterally because of tethering of the overlying epidermis to the underlying nodule (Figure 160-3).
- Usually asymptomatic but may be tender or pruritic.
- Size ranges from 0.3 to 10 mm; usually less than 6 mm. Rarely, DFs grow to larger than 5 cm.5
- May have a hyperpigmented halo and a scaling surface (Figure 160-4).
- DFs can rarely be located entirely within subcutaneous tissue.6
Dermatofibroma on the thigh of black woman. Note the darker brown halo around the lighter center. (Courtesy of Richard P. Usatine, MD.)
Pinch test showing a deep dimpling of ...