Excerpt from Dermatofibroma

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Background

Dermatofibroma (DF) is a common cutaneous nodule of unknown etiology that occurs more often in women. The lesion frequently develops on the extremities (mostly the lower legs) and is usually asymptomatic, although pruritus and tenderness are not uncommon. The latter feature is seen in a sufficient number of patients to make DF the most prevalent of all painful skin tumors. A number of well-described, histologic subtypes have been reported. Removal of the tumor is not necessary unless diagnostic uncertainty exists or particularly troubling symptoms are present.

Pathophysiology

The precise mechanism for the development of DF is unknown. Rather than a reactive tissue change, DF seems more likely to be a neoplastic process because of the persistent nature of the lesion and the demonstration that it is a clonal proliferative growth.¹ Clonality, of course, by itself, is not necessarily synonymous with a neoplastic process; it has been demonstrated in inflammatory conditions, including atopic dermatitis, lichen sclerosis, and psoriasis.

Immunohistochemical testing with antibodies to factor XIIIa is frequently positive in DF, while antibodies to MAC 387 show less consistent results. The former antibody labels fibroblasts (dermal dendrocytes), while the latter labels monocyte-derived macrophages (histiocytes). Controversy exists as to whether the factor XIIIa positivity occurs within the actual tumor cells of DF or simply labels the reactive stromal cells; hence, the cell of origin for the spindle cell proliferation of DF is debatable. The cell surface proteoglycan, syndecan-1, may play a role in the growth of DF.² Transforming growth factor-beta signaling might be a trigger of the fibrosis seen in DF.³

Frequency

United States

DF is relatively common.

International

Incidence is probably similar to that in the United States.

Mortality/Morbidity

DF is regarded as a benign lesion; however, discomfort from pain or itching may be significant. The few case reports of metastatic DF are disputable from the standpoint of histologic diagnosis. Such reported lesions were highly cellular, of large size, and locally recurrent.⁴ Indolent pulmonary metastases also were observed.

Race

Frequency appears to be similar in all races.

Sex

Females are affected more commonly than males, with a male-to-female ratio of 1:4.

Age

DF can occur in patients of any age, but it usually develops in young adulthood. Approximately 20% of the lesions occur before age 17 years.

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