SKINIPEDIA - Skin Essentials: Dermatofibroma

Skin Essentials: Dermatofibroma Study
Authors: Joseph C Pierson, MD, Consulting Staff, Department of Dermatology, Guthrie Army Clinic, Ft Drum, NY Coauthor(s): Christine C Tam, MD, Staff Physician, Dermatology Office of David A Spott, MD

Dermatofibroma is a common cutaneous nodule of unknown etiology that occurs more often in women. Dermatofibroma 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 dermatofibroma the most prevalent of all painful skin tumors. A number of well-described, histologic subtypes of dermatofibroma 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 dermatofibroma is unknown. Rather than a reactive tissue change, dermatofibroma 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. 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.

Results from immunohistochemical testing with antibodies to factor XIIIa, which label dermal dendritic cells, are frequently positive in dermatofibroma, while antibodies to MAC 387, which label monocyte-derived macrophages (histiocytes), show less consistent results. One study evaluated the expression in dermatofibroma of HSP47, a recently used marker for skin fibroblasts; CD68, a marker for histiocytes; and factor XIIIa. Most of the spindle-shaped cells in all 28 cases of dermatofibroma, irrespective of histologic variant, stained positively with HSP47, indicating that skin fibroblasts are a major constituent of dermatofibroma. Factor XIIIa–positive dendritic cells also are present, but the presence of CD68-positive histiocytes was inconsistent, especially between histologic variants.

The cell surface proteoglycan, syndecan-1, and fibroblast growth factor receptor 2, involved in epithelial-mesenchymal cross-talk, may play a role in the growth of dermatofibromas. Transforming growth factor-beta (TGF-beta) signaling might be a trigger of the fibrosis seen in dermatofibromas. TGF-beta, along with other fibrinogenic factors, may be produced by mast cells, which have been reported to occur in abnormally high numbers in dermatofibromas.

Frequency

United States - Dermatofibromas are relatively common.
International -Incidence of dermatofibroma is probably similar to that in the United States.

Mortality/Morbidity

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

One report describes a patient with a 9-cm subcutaneous deep fibrous histiocytoma who developed metastases and died. Deep fibrous histiocytoma has been regarded as a subset of dermatofibroma that arises in the subcutaneous or deep soft tissue, but the classification of the deep variant may evolve.

Race

Frequency of dermatofibroma appears to be similar in all races.

Sex

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

Age

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

Dermatofibroma Part II is here.

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