Dermatology

Dermatofibroma (Fibrous histiocytoma)

Are You Confident of the Diagnosis?

The diagnosis of dermatofibroma (DF), also referred to as fibrous histiocytoma, is made clinically and confirmed histologically if warranted. A patient history of a solitary, slow-growing cutaneous nodule on the extremities of young to middle-aged adults, often female, is consistent with DF. Usually these lesions are asymptomatic.

Characteristic findings on physical examination

Common DFs are usually less than 10mm in size and appear as dome-shaped papules, often with overlying hyperpigmentation. Upon lateral compression of these lesions a central dimple may be elicited, which is a helpful sign for clinical recognition of DF (Figure 1). Giant dermatofibromas have been described, ranging in size from 35 to 300mm. Other histologic variants of dermatofibroma include lipidized, hemosiderotic, keloidal, granular cell, palisading, atrophic, clear cell, myxoid, lichenoid, balloon cell, and signet-ring cell.

Figure 1.

A typical dermatofibroma demonstrating dimpling on lateral compression

The diagnosis of dermatofibroma can usually be made clinically, however, if warranted, definitive diagnosis is made by histologic analysis of a biopsy of the specimen. The dermatoscope may be useful in further visually characterizing a DF -- a peripheral pigment network with a central white area is the most common pattern seen under dermoscopy.

Expected results of diagnostic studies

Histologically, DF is defined by a proliferation of spindle cells that form short intersecting fascicles. Within this stroma, small capillaries and variable amounts of mature collagen are found. Inflammatory cells, histiocyte-like cells, foam cells, multinucleated giant cells, and siderophages may also be seen within the spindle cell collection. The presence of lesional cells surrounding individual collagen bundles (so called “collagen trapping”), if seen, is a useful diagnostic finding in DF. The epidermis overlying the spindle cells of DF is often hyperplastic and hyperpigmented in the basal layer (Figure 2).

Figure 2.

Dermatofibroma with basalar induction.

DF may sometimes extend into the superficial subcutis, at which time it may be difficult to differentiate from its malignant counterpart, dermatofibrosarcoma protuberans (DFSP). One point of differentiation is the tendency of DF to extend down the septae while DFSP extends diffusely. For further differentiation between the two entities, special staining of histologic specimens may be helpful. DF stains positively for Factor XIIIa and negative for CD34, while DFSP stains oppositely with positive CD34 staining and negative Factor XIIIa staining. This differentiation is, however, not absolute, as there are reports of Factor XIIIa positive DFSPs and of CD34 positive DFs.

Diagnosis confirmation

There is little value in imaging studies or serologic tests with solitary lesions of DF. However, the presence of multiple dermatofibromas (defined as at least 15), while most commonly a benign finding, can be indicative of a state of immune suppression and has been linked with HIV infection, myasthenia gravis, systemic lupus erythematosus, and diabetes. In these instances, further serologic testing may be indicated.

The differential diagnosis of DF is broad and includes the following entities: atypical fibroxanthoma, basal cell carcinoma, dermatofibrosarcoma protuberans, juvenile xanthogranuloma, leiomyoma, melanoma, neurilemmoma, nevus, pilomatrixoma, prurigo nodularis, scar and squamous cell carcinoma.

Who is at Risk for Developing this Disease?

DF may occur in any individual of either sex with no racial predilection. Women are much more likely to develop these lesions than men, with a 1:4 male:female ratio of dermatofibroma. DFs more commonly develop in young adults but can appear at any age.

What is the Cause of the Disease?

Etiology

Pathophysiology

The etiology of DF is unknown but appears to be a neoplastic (benign) rather than reactive tissue process. The clonal proliferative growth of these lesions, as well as the persistent nature of these growths, supports this viewpoint. Skin fibroblasts are the major cell constituent of DF.

Systemic Implications and Complications

DF are benign lesions and do not by themselves carry any significant systemic implications or complications. In one instance, the cellular variant of significant DF has been found to have indolent pulmonary metastases. As previously mentioned, the presence of multiple DFs (at least) may be indicative of a state of relative immune suppression that thus warrants further workup.

Treatment Options

Treatment options for DF are summarized in the Table 1

Table 1.

Treatment options for DF
Medical Treatment Surgical Procedures Physical Modalities
Topical corticosteroids with or without occlusion Cutaneous shaving None
Intralesional corticosteroids Excisional surgery
Cryotherapy Ablative surgery

Optimal Therapeutic Approach for this Disease

  • --Reassurance and watchful waiting is the optimal treatment in the majority of cases.

  • --If lesions are symptomatic, removal by cutaneous shaving, excisional surgery, or ablative laser surgery may be warranted.

  • --If lesions are symptomatic but the patient does not desire surgical intervention, topical or intralesional corticosteroids or cryotherapy may help relieve symptoms.

  • --If multiple (at least 15) lesions are present, further serologic testing for HIV infection, myasthenia gravis, systemic lupus erythematosus, and diabetes may be warranted.

Patient Management

Explanation of the benign nature of these lesions is usually all that is required for patient care. Further follow-up is not warranted unless there is clinical suspicion that the lesion may be something other than a DF. Lesions that continue to increase in size, become symptomatic, or change in symmetry, color, or begin to bleed should be biopsied. The presence of multiple lesions (at least 15) possibly warrants further systemic workup as detailed above.

Unusual Clinical Scenarios to Consider in Patient Management

DF is most often a benign condition that requires no further investigation or treatment. In cases of multiple (at least 15) lesions on a single patient, further investigation of possible immunosuppressive etiology may be indicated as this has been reported in both endogenous and exogenous causes of immunosuppression. A recent report mentions eruptive dermatofibromas in the setting of therapy with efalizumab. As always, if a lesion is changing in size, shape, color, or associated symptoms, biopsy may be warranted.

What is the Evidence?

Chen, TC, Kuo, T, Chan, HL. "Dermatofibromas is a clonal proliferative disease". J Cutan Pathol. vol. 27. 2000. pp. 36-9.

(An analysis of the growth origin of dermatofbromas.)

Fitzpatrick, TB, Gilchrest, B. "Dimple sign to differentiate benign from malignant pigmented cutaneous lesions". N Engl J Med. vol. 296. 1977. pp. 1518.

(A report on the use of the physically elicited “dimple sign” to differentiate benign from malignant lesions.)

Gershtenson, PC, Krunic, A, Chen, HM. "Multiple clustered dermatofibroma: case report and review of the literature". J Cutan Pathol. vol. 37. 2010. pp. e42-e45.

(A review of the implications of the occurrence of multiple dermatofibromas.)

Gonzales, S, Duarte, I. "Benign fibrous histiocytoma of the skin. A morphologic study of 290 cases". Pathol Res Pract. vol. 172. 1982. pp. 379-91.

(A large case study review of benign fibrous histiocytoma.)

Kimyai-Asadi, A, Goldberg, LH, Greenberg, C, Rabin, V, Parry, R, Batres, E. "Cellular, atypical, and indeterminate dermatofibromas; benign or malignant?". Dermatol Surg. vol. 34. 2008. pp. 1264-71.

(A review of the benign and maligant potential of DF.)

Kuroda, K, Tajima, S. "Proliferation of HSP47-positive skin fibroblasts in dermatofibroma". J Cutan Pathol. vol. 35. 2008. pp. 21-6.

(An analysis of the cellular origin of DF.)

Luzar, B, Calonje, E. "Cutaneous fibrohistiocytic tumors - an update". Histopathology. vol. 56. 2010. pp. 148-65.

(A review of the clinical and histologic features of DF and its variants.)

Nieyama, S, Katsuoka, K, Happle, R, Hoffmann, R. "Multiple eruptive dermatofibromas: a review of the literature". Acta Derm Venereol. vol. 82. 2002. pp. 241.

(A review of the significance of the presence of multiple DFs.)

Santos-Juanes, J, Coto-Sequra, P, Mallo, S, Galache, C, Soto, J. "Multiple eruptive dermatofibromas in a patient receiving efazlizumab". Dermatology. vol. 216. 2008. pp. 363.

(A case report of multiple DFs in a patient receiving efalizumab for psoriasis.)
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