Atrophic Dermatofibroma: A Unique Dermatofibroma Variant

Dermatofibromas are benign skin tumors with several variants, including the rare, uncommonly described atrophic dermatofibroma. To the best of our knowledge, there are currently 105 reported cases of atrophic dermatofibromas in the literature. This variant typically presents as a flat or depressed macule whose color can range from brown to white to red; in contrast to classic dermatofibromas that typically occur on the legs, atrophic dermatofibromas have a tendency to occur on the upper back and arms. An atrophic dermatofibroma can be clinically diagnosed; however, given the broad spectrum of clinical features of this lesion, a biopsy may be required. Characteristic pathologic features include epidermal acanthosis, basilar hyperpigmentation, fibroblast hyperplasia, and decreased or absent elastic fibers within the lesion. The pathogenesis of this lesion is not yet fully understood; however, it has been postulated that the loss of elastic fibers plays a key role in its development and characteristic atrophic appearance. We present the cases of two men with biopsy-confirmed atrophic dermatofibromas: a 47-year-old man with a pigmented macule on the right upper back and a 68-year-old man with an erythematous patch on the left posterolateral shoulder. The clinical and pathologic features of atrophic dermatofibromas are also summarized.

Atrophic dermatofibroma was first coined by Page and Assad in 1987; however, there are reports of similarly described lesions in the French and Spanish literature that predates 1987. This specific variant has been observed worldwide with retrospective studies estimating its prevalence to be as low as 0.5-2% to as large as 13-18%. These lesions typically present as smooth, umbilicated, skin-colored, or erythematous macules that are often misidentified on initial clinical examination [2][3][4].
Two men with skin lesions on the right upper back or left posterolateral shoulder were observed. The diagnosis of atrophic dermatofibroma was suspected clinically and confirmed on histologic evaluation. The clinical and pathologic features of this unique dermatofibroma variant are summarized. Microscopic evaluation of the tissue revealed epidermal acanthosis, basilar hyperpigmentation, and fibroblast proliferation on hematoxylin and eosin (H&E) staining ( Figure 2). Verhoeff-van Gieson (VVG) staining demonstrated a loss of elastic fibers in the lesion when compared to the adjacent dermis above, lateral, and below the tumor, which showed scant, black-stained elastic fibers ( Figure 3). Low (A) and higher (B) magnification of H&E-stained sections of an atrophic dermatofibroma shows a central depression (between blue arrows), epidermal acanthosis (thickening of the epidermis as shown between black bracket), basilar hyperpigmentation (yellow arrows), and a fibroblast proliferation (red circle) with trapped collagen bundles at the periphery (black arrows) (H&E: A, ×5; B, ×20). Low (A) and higher (B) magnification of VVG-stained sections of an atrophic dermatofibroma reveals a loss of black-stained elastic fibers (blue circle) within the lesion; in contrast, elastic fibers (black arrows) can be seen in the dermis above, adjacent, and deep to the dermal tumor. The red circle of image A is shown at higher magnification in image B (VVG: A, ×5; B, ×40).

VVG, Verhoeff-van Gieson
Correlation of the clinical features and pathologic findings established the diagnosis of an atrophic dermatofibroma. The benign nature of this lesion was discussed with the patient, and no further treatment was performed. The residual lesion will continue to be monitored clinically.

Case 2
A 68-year-old man with no significant personal or family history of dermatologic conditions or malignancies presented for an evaluation of his skin. Cutaneous examination revealed a 6.0 × 5.0-mm depressed, erythematous patch on his left posterolateral shoulder ( Figure 4). The clinical differential diagnosis included anetoderma, atrophic dermatofibroma, atrophoderma, dermatofibrosarcoma protuberans, and granuloma annulare. A punch biopsy was performed. Microscopic evaluation of the tissue specimen revealed epidermal acanthosis, heavy melanin deposits in the basilar layers of the epidermis, and focal fibroplasia in the dermis on H&E-stained sections ( Figure 5). VVGstained sections revealed an absence of elastic fibers within the lesion; however, they were present in the dermis above, adjacent to and below the lesion ( Figure 6). Low (A) and higher (B) magnification of VVG-stained sections of an atrophic dermatofibroma reveals an absence of elastic fibers within the tumor (red circle); however, black-stained elastic fibers (yellow arrows) can be visualized in the deep dermis above, adjacent, and deep to the dermatofibroma (VVG: A, ×5; B, ×20).

VVG, Verheoff-van Gieson
Correlation of the clinical and pathologic findings established the diagnosis of an atrophic dermatofibroma. The benign nature of the lesion was discussed, and no further treatment was performed.
The residual lesion will continue to be monitored clinically.

Discussion
Atrophic dermatofibroma is a less frequently described variant compared to the common fibrous dermatofibroma. To the best of our knowledge, this lesion has been reported in the literature in approximately 107 patients, including our two patients presented above. There were 55 women and 14 men, establishing a female-to-male ratio of 3.9 to 1.0. Gender was not disclosed for 38 individuals [2,[5][6][7].
This rare fibrohistiocytic tumor was most commonly diagnosed in patients 40-49 years old; no known association between atrophic dermatofibroma and other cutaneous or systemic diseases has been identified. Unlike classic dermatofibromas that typically occur on the lower extremities, this rare variant is most common on the upper back and arms. Given its rarity and atypical presenting locations, it has been reported that the mean time from onset to diagnosis ranges between three and eight years [2,4,8].
Atrophic dermatofibroma is a benign tumor that typically presents as a flat, atrophic solitary lesion whose color can vary from flush white to red to brown. The size ranges from 5.0 × 7.0 mm to 5.0 × 5.0 cm. Typically, the lesion is asymptomatic; however, some patients have noted changes in size, associated pain, and intermittent swelling [2].
Dermoscopy has been reported as a possible tool to aid in proper clinical diagnosis of this rare variant. Dermoscopic findings of atrophic dermatofibroma include a patchy, peripheral pigment network with multiple white patches. With increased data collection and observation, dermoscopy may play an important role in accurate clinical identification of this uncommon tumor; however, because the clinical expertise of dermoscopy is dependent on the individual performing the evaluation, biopsy of a lesion that is morphologically suspected to be an atrophic dermatofibroma may be helpful to establish the diagnosis [4,[9][10][11].

Condition
Although a central depression can occasionally be observed in common dermatofibromas, early researchers have suggested that the central depression in atrophic dermatofibromas must be severe, measuring greater than 50% in the locoregional dermis. The central depression and atrophic appearance of the lesion have been associated with the decrease or complete loss of elastic fibers in the lesion with a normal distribution of elastic fibers at the periphery; this is most readily seen on VVG-stained sections. Both of our patients had a significant decrease in elastic fibers within their lesions with normal-appearing distribution of elastic fibers in the dermis above, adjacent to and beneath the atrophic dermatofibroma [1,2,8,10,11].
The pathogenesis of atrophic dermatofibroma remains to be elucidated. However, it has been postulated that the loss of elastic fibers plays an integral role in the development of the lesion and its dimpled, atrophic appearance. Furthermore, it has been reported that the paucity of elastic fibers may be due to elastophagocytosis by dermatofibroma cells and/or elastolysis caused by overexpression of matrix metalloproteinase-1 in the tumor cells [2,6,11].
Another postulated mechanism for the atrophic clinical appearance of this lesion may be related to the subcutaneous tissue atrophy present beneath the lesion. However, deep tissue samples are not typically included in the submitted biopsy specimen; therefore, observation to confirm this is limited. Hence, loss of elastic fibers or subcutaneous tissue biopsy or both may have a role in the development of atrophic dermatofibroma [2,6,11].
Atrophic dermatofibromas are benign lesions. If clinically diagnosed, no further intervention is necessary. If the diagnosed is established histologically and a portion of the tumor has been removed, it is reasonable to periodically monitor the residual lesion [2].

Conclusions
Atrophic dermatofibroma is an uncommon, benign variant of a dermatofibroma. There are 107 cases described, and the tumor occurs almost four times more often in women than men. Moreover, we suspect that the prevalence of this lesion is greater than the number of reported cases in the literature as the lesion may be misdiagnosed because of its atypical presentation. Atrophic dermatofibroma typically presents as an erythematous or hypopigmented, atrophic macule on the upper back and arms. The clinical differential diagnosis of atrophic dermatofibroma is broad and includes benign and malignant neoplasms, local dermatoses, and systemic conditions. The diagnosis can be suspected clinically based on clinical features and confirmed histologically with microscopic examination of a tissue specimen. Characteristic histologic findings include the loss of elastic fibers, dermal thinning, and central depression which may be greater than 50% in the locoregional dermis. In our patients, atrophic dermatofibroma was clinically suspected and confirmed on evaluation of the biopsy tissue specimen. Because an atrophic dermatofibroma is benign, excision is not required if the tumor is clinically diagnosed. Periodic monitoring of the residual lesion can be considered if a partial biopsy of the lesion was performed.

Additional Information Disclosures
Human subjects: Consent was obtained or waived by all participants in this study. Conflicts of interest: In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: All authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. Other relationships: Philip R. Cohen is a consultant for ParaPRO.