Dermatofibroma: Atypical Presentations.

Dermatofibroma is a common benign fibrohistiocytic tumor and its diagnosis is easy when it presents classical clinicopathological features. However, a dermatofibroma may show a wide variety of clinicopathological variants and, therefore, the diagnosis may be difficult. The typical dermatofibroma generally occurs as a single or multiple firm reddish-brown nodules. We report here two atypical presentations of dermatofibroma - Atrophic dermatofibroma and keloidal presentation of dermatofibroma. Clinical dermal atrophy is a common phenomenon in dermatofibromas as demonstrated by the dimpling on lateral pressure. However, this feature is exaggerated in the atrophic variant of dermatofibroma. Atrophic dermatofibroma is defined by dermal atrophy of more than 50% of the lesion apart from the usual features of common dermatofibroma. The keloidal variant of dermatofibroma should not be overlooked as a simple keloid. The findings of keloidal change in dermatofibromas may support that trauma is a possible cause of dermatofibroma.

What was known?

Keloidal and atrophic dermatofibroma are rare variants of cutaneous fibrous histiocytoma.

Introduction

Dermatofibroma is a benign cutaneous tumor due to reactive fibroblastic proliferation. The typical dermatofibroma generally occurs as a single or multiple skin color to reddish-brown or dark brown firm nodule located most commonly at lower legs in the middle-aged individuals with slight female preponderance. The surface is often acanthotic and on the side to side pressure with two fingers elicits the characteristic “dimple sign” due to tethering of the overlying epidermis to the underlying lesion. We report here two atypical presentations of dermatofibroma - Atrophic dermatofibroma and keloidal presentation of dermatofibroma. Atrophic and keloidal dermatofibromas are well-described, but uncommon, variants of dermatofibroma. We, therefore, want to emphasize that dermatofibroma can present in unusual forms also apart from the classical presentation. The aim of this communication is to bring to attention these clinical entities.

Case Reports

Case 1

A 30-year-old female presented with a single asymptomatic depressed lesion on her left leg since 3 years. She did not have any episode of local trauma or injection. Her past and family history was also unremarkable. Physical examination revealed a relatively well demarcated, single, asymptomatic, 10 mm × 8 mm indurated, atrophic, and depressed lesion adherent to the subcutaneous tissue over lateral aspect of left lower limb [Figure 1]. A clinical diagnosis of panniculitis was made. A punch biopsy was done. Histopathological examination revealed a well-defined fibrohistiocytic dermal tumor with epidermal hyperplasia [Figure 1a]. There was thinning of the involved dermis compared to adjacent normal skin with 50% reduction in thickness of dermis. The atrophic dermis contained haphazardly arranged spindle cells [Figure 1b]. There was no atypia. Atrophic dermatofibroma was diagnosed.

Figure 1

Single, well demarcated, 10 mm × 8 mm indurated, atrophic, and depressed lesion adherent to the subcutaneous tissue over lateral aspect of left lower limb. (c) Microphotograph showing epidermal hyperplasia (H and E, ×40). (b) Microphotograph showing dermis containing haphazardly arranged spindle cells. There was no atypia (H and E, ×40)

Case 2

A 30-year-old female presented with a mild pruritic firm hyperpigmented cord like lesion over the left lateral side for last 3 years. Initially, it started as a dome-shaped papule that gradually progressed in size to become the present size of 7 cm × 2 cm. For last 10 years, she had a multiple painless dome shaped firm, nodular eruptions of 2–3 cm size in various sites. There was no history of trauma preceding the onset of the lesion present. She did not have any history of evening rise of temperature or chest symptoms. In the family history, her mother had single keloidal lesion over the chest. In the treatment history, she had applied high potent topical steroid application for several months but without any improvement. (She had also received intralesional triamcinolone injection for several times.) Personal history was nothing significant. Physical examination revealed 7 cm × 2 cm size cord like plaque over the left lateral side. The overlying skin was hyperpigmented, puckered, and attached with the underlying lesion as on lateral pressure the skin is stretched. There was atrophy of the surrounding skin following prolonged application of topical as well as intralesional steroid [Figure 2]. A clinical diagnosis of keloid, lupus vulgaris, and sarcoidosis were kept, and punch biopsy was done. Histopathologic examination showed a well-defined fibrohistiocytic dermal tumor with epidermal hyperplasia [Figure 2a]. The dermis contained haphazardly arranged spindle cells [Figure 2b]. There was no atypia. Dermatofibroma with the keloidal presentation was diagnosed.

Figure 2

Single, 7 cm × 2 cm size cord like plaque over left lateral side of chest wall with overlying hyperpigmented, puckered skin and atrophy of the surrounding skin. (a) Microphotograph showing epidermal hyperplasia (H and E, ×40). (b) Microphotograph showing dermis containing haphazardly arranged spindle cells. There was no atypia (H and E, ×40)

Discussion

Dermatofibroma (cutaneous benign fibrous histiocytoma) is a slow growing firm nodule. The typical dermatofibroma generally occurs as a single or multiple firm reddish-brown nodules.[1] It usually occurs on the lower extremities of young to middle-aged women. Apart from the classical feature, different variants have been described. Atrophic and keloidal dermatofibromas are well described, but uncommon variants of dermatofibroma.

Atrophic dermatofibroma, first described by Page and Assaad[2] in 1987 is a rare variant of dermatofibroma. Atrophic dermatofibroma represents approximately 2% of all dermatofibroma.[3] Atrophic dermatofibroma tends to occur on the upper trunk and upper extremities of middle-aged women (40–50 years).[34] Clinical dermal atrophy is a common phenomenon in dermatofibromas as demonstrated by the dimpling on lateral pressure.[5] However, this feature is exaggerated in the atrophic variant of dermatofibroma.[2] This is due to focal loss of elastic fibers due to “elastophagocytosis” by the dermatofibroma cells.[6] Atrophic dermatofibroma is defined by dermal atrophy of more than 50% of the lesion apart from the usual features of common dermatofibroma.[6] This variant of dermatofibroma should be considered in the diagnosis of inwardly puckered, depressed lesions.[5]

Again the keloidal presentation of dermatofibroma should not be overlooked as a simple keloid. The Asian people are more prone to develop a keloid.[7] The findings of keloidal change in dermatofibromas may support that trauma is a possible cause of dermatofibroma.[7]

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

What is new?

Atrophic and keloidal variant of dermatofibroma are rare clinico-pathological entities and should be differentiated from keloid or other atrophic cutaneous conditions.