Introduction

An atrophic dermatofibroma—a variant of a dermatofibroma—is an uncommon benign fibrohistiocytic tumor that usually presents in adults as an asymptomatic depressed plaque [1,2,3,4]. A comprehensive review of the literature was performed using the PubMed database to search the words: atrophic dermatofibroma; the relevant papers and their references generated by the search were reviewed. The features of this unique neoplasm are presented. Informed consent was obtained from the two participants for inclusion in this study. The patients also signed a consent form providing permission to include relevant clinical photographs in this article.

Discussion

Dermatofibromas

Dermatofibromas are benign tumors consisting of fibroblasts and histiocytes [1,2,3,4]. They typically occur as solitary lesions; however, multiple dermatofibromas can be associated with various conditions [5]. Several clinical and pathological variants of a dermatofibroma have been described (Table 1) [2,3,4, 6,7,8,9,10,11]. An atrophic dermatofibroma is a rare subtype of dermatofibroma [7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30].

Table 1 Variants of a dermatofibroma
Full size table

History

Page and Assad are credited with introducing the term ‘atrophic dermatofibroma’ in 1987 when they described the features of three women with this variant of a dermatofibroma in the Journal of the American Academy of Dermatology [16]. However, in a subsequent paper on this topic, Curco et al. [19] cited another article in the Spanish dermatology literature that was published in 1975 by Gabrielli et al. [15] that reported three women with dermatofibromas that originally appeared as indurated nodular lesions and spontaneously involuted with subsequent clinical and pathology features of an anetoderma. In addition, in Gabrielli et al.'s [15] paper, the authors acknowledge previously published papers in the French literature (from 1960 by Temime and Oddoze [12] and 1964 by Lefranc and Simard [13]) and Spanish literature (from 1968 by Arguelles-Casals and Rodriguez [14]) that described patients with similar lesions.

Significant contributions to the atrophic dermatofibroma literature are summarized in Table 2 [7,8,9, 11,12,13,14,15,16,17,18,19,20,21,22,23,24]. In this article, we summarize the world literature on this subject. We also present two men with atrophic dermatofibromas in the legends accompanying the figures in this paper (Table 3). They range in age from 45 to 64 years (median age, 55 years). Their fibrohistiocytic lesions are located on their proximal extensor arm (Figs. 1, 2, 3) and upper back (Figs. 4, 5, 6).

Table 2 Significance of atrophic dermatofibroma publications
Full size table
Table 3 Clinical and pathologic features of two men with an atrophic dermatofibroma
Full size table
Fig. 1
figure 1

Atrophic dermatofibroma: left shoulder of a 45-year-old Caucasian man. Distant (a) and closer (b) views of an asymptomatic lesion on the left shoulder of more than 3 years of duration. There was no prior history of trauma or injection to the site. As a youth, he had cystic acne. The lesion appeared as a 15 × 15-mm flesh-colored indurated patch surrounding a 10 × 10-mm telangiectatic depressed central area; the lesion is outlined by the purple lines (b). Squeezing the edges of the lesion between the examiner’s thumb and index finger produced a dimpling of the central portion of the lesion. The submitted clinical differential diagnosis was an atrophic dermatofibroma

Full size image
Fig. 2
figure 2

Atrophic dermatofibroma on the left shoulder of a 45-year-old Caucasian man: pathology features of hematoxylin and eosin-stained sections. Low magnification (a) and higher magnification (b, c) views of a 3-mm punch biopsy from the central portion of the depressed area show epidermal acanthosis (between blue arrows) with basal layer hyperpigmentation (black arrows) (a, b). There is atrophy of the dermis, and the dermal tumor shows an increased number of fibroblasts with trapped collagen bundles in the periphery (hematoxylin and eosin: a ×2; b ×4; c ×20)

Full size image
Fig. 3
figure 3

Atrophic dermatofibroma on the left shoulder of a 45-year-old Caucasian man: pathology features of Verhoeff-Van Gieson-stained sections. Low magnification (a) and higher magnification (b, c) views of a 3-mm punch biopsy from the central portion of the depressed area show an absence of elastic fibers in the tumor. However, elastic fibers (which stain black and are demonstrated by black arrows) can be noted in the deep dermis beneath the dermatofibroma (a, c) (Verhoeff-Van Gieson: a ×2; b ×20; c ×20)

Full size image
Fig. 4
figure 4

Atrophic dermatofibroma: left upper back of a 64-year-old Caucasian man. Distant (a) and closer (b) views of an asymptomatic lesion on the left upper back of 1-year duration that had been noticed by his wife. There was no prior history of trauma or injection to the site. The lesion appeared as a 6 × 6-mm flesh-colored depressed area; the lesion is outlined by the purple lines (b). The submitted clinical differential diagnosis was an atrophic dermatofibroma

Full size image
Fig. 5
figure 5

Atrophic dermatofibroma on the left upper back of a 64-year-old Caucasian man: pathology features of hematoxylin and eosin-stained sections. Low magnification (a) and higher magnification (b–d) views of an 8-mm punch biopsy show a depressed area in the central portion of the specimen (between white arrows). The epidermis has seborrheic keratosis-like hyperplasia (between blue arrows) (a, b) and hyperpigmentation of the basal layer (black arrows) (a–c). The center depression reveals atrophy of the dermis (a, b). The dermal tumor consists an increased number of fibroblasts with trapped collagen bundles in the periphery (a–d) (Hematoxylin and eosin: a ×2; b ×4; c ×20; d ×10)

Full size image
Fig. 6
figure 6

Atrophic dermatofibroma on the left upper back of a 64-year-old Caucasian man: pathology features of Verhoeff-Van Gieson-stained sections. Low magnification (a) and higher magnification (b–d) views of an 8-mm punch biopsy show an absence of elastic fibers in more than 90% of the dermatofibroma. Elastic fibers (which stain black and are demonstrated by black arrows) are only present in the superficial portion of the tumor in the papillary dermis (a–d). In addition, black staining of elastic fibers (black arrows) can be observed in the deep dermis beneath the dermatofibroma (a, b) (Verhoeff-Van Gieson: a ×2; b ×4; c ×10; d ×20)

Full size image

Geographic Distribution

Atrophic dermatofibromas have been observed worldwide; indeed, publications describing individuals with this lesion have originated from Argentina [15], Austria [9], Brazil [26], Canada [16], Cuba [14], France [12, 13], Germany [7], India [28], Italy [23], Japan [17, 18], Korea [20, 25], Mexico [11, 21], Portugal [27], Spain [8, 19], Turkey [22] and the United States [10, 24, 29, 30]. Most of the articles (14 of 24, 58%) on atrophic dermatofibromas describe one individual [10, 12, 13, 17,18,19,20,21,22, 24, 26, 28,29,30]; including our paper, two or three patients are reported in six manuscripts (25%) [8, 15, 16, 25, 27]. There are only four larger series (17% of the publications on atrophic dermatofibromas) which range from 15 to 26 patients [7, 9, 11, 23].

Incidence

The incidence of atrophic dermatofibromas, as compared to other variants of a dermatofibroma, has been evaluated by five groups of investigators (Table 4) [9, 11, 23, 27, 30]. Three of the research groups discovered the incidence to be very low, at less than 2% [9, 27, 30]. Specifically, the incidence ranged from 0.5% (1 of 214 lesions) to 1.7% (26 of 1526 lesions); combining the 3 studies showed the incidence to be 1.5% (29 of 1932 lesions).

Table 4 Incidence of atrophic dermatofibromas
Full size table

However, more recently, two studies demonstrated a much higher incidence ranging from 14 to 18%; however, in these investigations, a pathology confirmation of the diagnosis was not confirmed [11, 23]. If the definitive diagnosis of an atrophic dermatofibroma was based upon the pathologic criteria of more than a 50% reduction of dermal thickening beneath the lesion [9], it is possible that the higher incidence of atrophic dermatofibromas that the later investigators noted may have been over-estimated since some of their diagnoses were only determined by the clinical appearance of the lesion [11, 23]. Indeed, when one of the groups of earlier investigators were screening 1526 dermatofibroma pathology specimens, they observed a minimum of 16.4% (more than 250) dermatofibromas with dermal atrophy of less than 50% of the surrounding dermis and did not include the lesions in their study of 26 atrophic dermatofibromas which resulted in the significantly lower incidence that they recorded of 1.7% [9].

Epidemiology

Atrophic dermatofibromas have been described—including the two individuals in this report—in 102 patients [7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30]. Several of the reports did not provide the patient’s gender or other clinical features [11,12,13,14, 22, 23, 27]. However, demographic information was provided for 64 individuals with atrophic dermatofibroma (Tables 5 and 6) [7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30].

Table 5 Clinical characteristics of 53 women with an atrophic dermatofibroma
Full size table
Table 6 Clinical characteristics of 11 men with an atrophic dermatofibroma
Full size table

Atrophic dermatofibromas occur more often in women (53/64, 83%) than men (11/64, 17%). The ratio of women to men is nearly 5:1. Similarly, a female prevalence has also been observed in individuals with other types of dermatofibromas, ranging from 2.2:1 [31] to 2.6:1 [3] to 5:1 [9].

The age—when the diagnosis of atrophic dermatofibroma was established—ranged from 12 to 86 years (median, 45 years). The women ranged in age from 12 to 86 years (median, 48 years). The men ranged in age from 27 to 78 years (median, 40 years).

Duration

The duration of time that the atrophic dermatofibroma was noted prior to establishing the diagnosis was described in 11 women (Table 5) [7,8,9,10,11,12,13,14,15,16,17,18, 21,22,23, 25,26,27,28,29] and 5 men (Table 6) [7,8,9, 11,12,13,14, 19, 20, 22,23,24, 27, 30]; also, the average duration of the lesion was 5.8 years in an additional 11 patients [7]. Therefore, the dermatofibroma was present from 3 to more than 40 years (median, 8 years) in the women and from 1 to 20 years (median, 3 years) in the men before the diagnosis was confirmed. Overall, for the 31 patients in whom this information was provided, the tumor was initially observed between 1 to more than 40 years (median, 6 years) prior to diagnosis.

Symptoms

Atrophic dermatofibromas are usually asymptomatic. However, some of the patients noted their lesion to either be painful (Table 6, cases 1 and 5) or increasing in size caused by either progressive enlargement or swelling (Table 5, case 32 and Table 6, case 1, respectively). None of the patients had a history of trauma or insect bite or steroid injection to the location.

Clinical Presentation

Atrophic dermatofibromas typically presented as a solitary patch with a central umbilication. However, some of the pathology-confirmed atrophic dermatofibromas presented as nodular lesions [7, 11]. In addition, at least 4 women (Table 5, cases 7, 19, 23, and 31) [15, 26] and one man (Table 6, case 3) [24] had multiple tumors. The 33-year-old man’s lesions presented as an agminated cluster of tumors, which occasionally itched, on his left thigh [24].

The size of the tumor varied from 5 × 7 mm [10] to 5 × 5 cm [19]. The texture of the patch was either indurated or soft or similar to that of the surrounding skin. Its appearance also varied; the patch was either flesh-colored, brown or erythematous.

Location

The location of the atrophic dermatofibromas, in 64 patients in whom the site was provided, are summarized in Table 7 [7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30]. Most of the lesions (46, 72%) were found above the waist. Only 28% (18) of the tumors were located on legs or buttocks.

Table 7 Location of atrophic dermatofibromas in 64 patients
Full size table

The most common locations of atrophic dermatofibromas were the shoulder (16 patients, 25%; Fig. 1), the lower extremity (15 patients, 23.4%) and the back (11 patients, 17.2%; Fig. 4). The lesions were also observed on the arm (six patients, 9.4%), the trunk (five patients, 7.8%) and the breast (four patients, 6.2%). The axilla (three patients, 4.7%), the buttock (three patients, 4.7%) and the neck (one patient, 1.6%) were less frequent sites.

The atrophic dermatofibroma site varied in the 40 women and 9 men for which the location was given. Similar to women with non-atrophic dermatofibromas, the lower extremity was the most common location (10, 25%); other frequent sites included the shoulder (9, 22.5%) and the back (7, 17.5%). However, in the men, the back (4, 44.5%) and the thigh (2, 22.2%) were the predominant locations.

Dermoscopy

Dermatoscopic features most often observed in common fibrous dermatofibromas include a central white patch and a pigment network [12, 23, 31]. However, the features of atrophic dermatofibromas—included in the studies of multiple dermatofibromas—were described by three groups of investigators [11, 22, 23]. All observed the same patterns.

A single individual with an atrophic dermatofibroma was included in a study of 52 dermatofibromas from 37 patients. The morphologic presentation was a 1.2 × 1.0-cm atrophic plaque; the suspected clinical diagnosis was a morpheaform basal cell carcinoma. Multiple small scar-like areas and a patchy distribution pigment network (that was prominent at the periphery) were observed with dermoscopy; therefore, the diagnosis of a melanocytic neoplasm was entertained dermoscopically. However, pathology revealed an atrophic dermatofibroma [22].

Both of the latter groups of investigators confirmed the previously described dermoscopic observations. Specifically, in 10 of 16 atrophic dermatofibromas (from a group of 130 dermatofibromas in 115 patients), a dermatoscopic pattern of multiple white scar-like patches was noted; the researchers also commented that this pattern of multiple white scar-like patches could be observed in dermatofibromas with sebaceous hyperplasia [23]. The other researcher’s evaluation of 100 dermatofibromas from 95 patients revealed that 17 atrophic dermatofibromas not only had a dermoscopic pattern of patchy pigment network but also a pattern of white patches [11].

A 40-year-old woman with a combined (aneurysmal and atrophic) dermatofibroma [6] on her upper arm was described. Her 1.5-cm tumor presented as a non-tender erythematous atrophic plaque. In addition to a pigment network and scar-like white patches, dermoscopy revealed arborizing vessels arising from a bluish homogenous area resembling a flame pattern [21].

Dermoscopic features of an atrophic dermatofibroma on the right mid-back of a 64-year-old man were also reported. The 12 × 8-mm indented red plaque showed a poorly defined erythematous lesion with a stellate white scar-like area and white-to-yellow lobules. The latter pattern of lobules corresponded to sebaceous hyperplasia induced by the dermatofibroma [30].

Pathology

Hematoxylin and Eosin Staining

The histopathology of common fibrous dermatofibroma is characterized by a proliferation of spindle-shaped fibroblasts in the dermis; histiocytes, collagen and blood vessels are also present. The fibrous cells often are arranged in a storiform, whirling pattern. A zone of normally appearing collagen in the papillary dermis (Grenz zone) is often present between the overlying epidermis and the dermal lesion [1,2,3,4].

The epidermis is frequently acanthotic. Indeed, it may mimic the appearance of a seborrheic keratosis. In addition, hyperpigmentation of the epidermal basal layer, induction of basal cell carcinoma-like features, hair follicle formation or sebaceous hyperplasia may be present [1,2,3,4].

In addition to the common fibrous dermatofibroma, there are several other variants of a dermatofibroma (Table 1) [2,3,4, 6,7,8,9,10,11]. Each of these has its own unique and distinctive pathologic features. Although the clinical presentation of an atrophic dermatofibroma can often be differentiated from that of a common fibrous dermatofibroma, the pathologic changes observed in the atrophic variant shares several similarities with those noted in a common fibrous dermatofibromas.

Page and Assaad's initial description of ‘atrophic dermatofibroma’ in 1987 was based the clinical presentation of the tumors—either an atrophic plaque or a pit-like depression or a depressed patch. Two of the three lesions demonstrated extreme cellularity which the investigators postulated explained the typical sinking in of the biopsy punch into the lesion. However, the third atrophic dermatofibroma, on the breast of a 46-year-old woman, showed pathologic changes of a typical fibrous dermatofibroma [16].

The next study, by Beer et al. in 1991, of 15 atrophic dermatofibromas revealed similar features in all of the tumors: at low magnification, there was acanthosis and papillomatosis of the epidermis, depression of the central surface and thinning of the dermis; however, the extent of dermal thinning was not quantified. Epidermal changes similar to those noted in common fibrous dermatofibromas—follicular differentiation (five cases), sebaceous differentiation (four cases) and basal cell carcinoma-like changes (three cases)—were also present. All of the tumors penetrated into the subcutaneous fat. The investigators arbitrarily defined two atrophic dermatofibroma histologic subtypes: moderately atrophic type (which had only moderate thinning of the dermis) and pronounced atrophic type (which had pronounced thinning of the reticular dermis, collagen bundle homogenization and decreased cellularity) [7].

In contrast to these earlier researchers, Requena and Reichel did not observe any dermal atrophy in their microscopic evaluation of the atrophic dermatofibromas from two women. Instead, they only observed a central dell; there was no thinning or loss of preexisting collagen bundles in the dermis. Hence, they attributed the clinical appearance of atrophy to be the result of a central depression instead of authentic atrophy [8].

However, in 1995, Zelger et al. suggested that the predominant histopathologic feature of an atrophic dermatofibroma should be dermal atrophy of more than 50% of the locoregional dermis. They described the features of 25 patients with an atrophic dermatofibroma. They also commented that during the screening of lesions to include in their study, they encountered more than 250 dermatofibromas with dermal atrophy of less than 50% [9].

A combined dermatofibroma is a dermatofibroma that demonstrates the coexistence of two variant patterns in a single lesion [6]. Three patients (two men [19, 20] and one woman [21]) had combined (atrophic and aneurysmal) dermatofibromas. The tumors were on the back [20], upper trunk [19] and upper arm [21]. The woman’s lesion was asymptomatic [21]; however, both of the men’s tumor was painful [19, 20].

Our patients had epithelial hyperplasia (either acanthosis or seborrheic keratosis-like proliferation of the epidermis), basal layer hyperpigmentation of the epidermis, and a depression in the center portion of the specimen (Figs. 2 and 5). In addition, both men had dermal atrophy (Table 3); this is more readily observed in the lesion from the left upper back of the 64-year-old man (Fig. 5). The dermal tumor shows an increased number of fibroblasts with trapped collagen bundles in the periphery.

Elastic Fiber Staining

Several investigators have noticed that elastic fibers are either decreased or absent in atrophic dermatofibromas [17, 18, 26, 30]. In contrast, Curco et al. observed normal elastic fibers in the combined dermatofibroma (with features of both an atrophic and aneurysmatic dermatofibroma) of 10-years duration on the left upper trunk of a 40-year-old man [19]. However, in non-atrophic dermatofibromas, some of the researchers also observed decreased elastic fibers [6, 8], whereas other investigators noted that the elastic fibers were increased in older lesions [32].

Zelger et al. evaluated 25 atrophic dermatofibromas. They performed Verhoeff-Van Gieson’s staining on some of their specimens. However, they did not report the results [9].

Kiyohara et al. reported a 55-year-old woman with a 9 × 7-mm atrophic dermatofibroma of 6.5-years duration that presented as a relatively well demarcated, slightly elevated, dark red, oval plaque on her left upper back. The Verhoeff-Van Gieson elastic stain did not reveal any elastic fibers between the collagen fibers of the dermatofibroma compared with those observed in the adjacent normal skin. The researchers also evaluated four non-atrophic dermatofibromas; all of these also showed decreased—but not complete loss—of elastic fibers [17].

Ohnishi et al. described a 69-year-old woman whose atrophic dermatofibroma presented as a relatively well-demarcated, light brown, intracutaneous nodule. The left thigh lesion measured 23 × 15 mm; there was a 11 × 8-mm crateriform depression in the center of the lesion. The Verhoeff-Van Gieson stain showed greatly decreased or complete disappearance of the elastic fibers in the atrophic area of the lesional dermis; however, a dense presence of elastic fibers was observed around the medium-sized vessels in the lesional lower dermis [18].

Ohnishi et al. also evaluated eight non-atrophic dermatofibromas: three cellular benign fibrous histiocytomas, three histiocytic cellular variants and two intermediate types. In comparison to the presence of elastic fibers in the marginal areas, the fibers were completely absent in the three fibrous dermatofibromas and reduced by 20–30% in one of the five other dermatofibromas. Only one of the eight dermatofibromas showed elastic fibers around the vessels [18].

Mota et al. described a 57-year-old woman with a brown, mildly pruritic, well-defined, firm, 3 × 2-cm patch with an atrophic surface on her left flank of 10-years duration. The orcein elastic stain revealed an absence of elastic fibers in the middle of the lesion [26].

Morse et al. reported a 64-year-old man with a 12 × 8-mm indented, erythematous plaque with an ill-defined border on his right mid-back. The Verhoeff-Van Gieson elastic stain revealed a diffuse reduction of elastic tissue. However, there was an aggregation of elastic fibers at the periphery [30].

Our patients’ atrophic dermatofibromas both had either absent or decreased elastic fibers in the tumor (Table 3). The 45-year-old man with the left shoulder atrophic dermatofibroma had no elastic fibers in his tumor; however, elastic fibers were observed in the dermis beneath the dermatofibroma (Fig. 3). The 64-year-old man with the left upper back atrophic dermatofibroma had an absence of elastic fibers in more than 90% of the tumor; elastic fibers were noted not only in the superficial portion of the tumor in the papillary dermis, but also—similar to our other patient—in the dermis beneath the dermatofibroma (Fig. 6).

Immunohistochemistry

Immunohistochemical staining may be used to differentiate dermatofibromas from dermatofibrosarcoma protuberans. Factor XIIIa and cluster of differentiation 34 (CD34) staining are often performed. Dermatofibromas demonstrate positive staining with factor XIIIa and an absence of staining with CD34; in contrast, dermatofibrosarcoma protuberans are not stained with factor XIIIa and show positive staining with CD34 [2,3,4, 33, 34].

Factor XIIIa and CD34 were evaluated in a study of 26 cases of atrophic dermatofibroma. Positive staining for factor XIIIa (ranging from 10 to 50%) was noted in 20 (73%) of the cases; there was absence of staining for 6 of the women’s tumors. However, 2 of the factor XIIIa-positive tumors also stained with CD34: 25% positivity of a lesion on the thigh of a 32-year-old man and 75% positivity of a lesion on the axilla of a 66-year-old woman [9].

Factor XIIIa was also positive in other women [10, 17, 21, 26, 29] and men [19, 24] whose atrophic dermatofibromas were evaluated. Yet, one man’s tumor—a 27-year-old with an atrophic dermatofibroma of 2-years duration on his back—was factor XIIIa-negative [20].

Focal CD34-positive staining was also observed in atrophic dermatofibromas of two additional women [10, 29] and one man [20]. One woman was 45-years old with a right axilla tumor, and the other woman was 64-year-old with a left thigh tumor; the latter woman’s atrophic dermatofibroma had been present for more than 40 years. The man was the 27-year-old whose back tumor of 2-years duration was also factor XIIIa-negative [20].

The etiology of the unexpected absence of factor XIIIa expression and the aberrant CD34 staining remains to be determined. In old dermatofibromas, factor XIIIa immunoreactivity may be lost as a result of increasing sclerosis and fibroblast-like differentiation of dendrocytes [10]. Positive staining for CD34 in atrophic dermatofibromas may be secondary to a background/demarcation phenomenon; this results when the background is rich in small, flattened vessels and nonspecific staining with CD34 occurs [9, 10, 19].

Electron Microscopy

The atrophic dermatofibroma on the left upper back of a 55-year-old woman was examined. The ultrastructural examination coincided with the light microscopy observations: only a few elastic fibers were found in the extracellular spaces of the dermatofibroma. However, intracellular elastic fibers—surrounded by double membranes—were noted within the tumor cells of the dermatofibroma [17].

Differential Diagnosis

The clinical differential diagnosis of atrophic dermatofibromas includes benign and malignant neoplasms, reactive dermatoses and systemic diseases (Table 8) [7,8,9,10, 15, 16, 18,19,20,21, 24,25,26, 28,29,30, current report]. Seventy-nine diagnoses were suggested by the clinicians who biopsied 52 of the patients; there were 12 patients (11 women and 1 man) for whom a clinical diagnosis was not stated. For those individuals in whom the information was available (37 patients), the number of diagnoses submitted ranged from one (27 patients) to six (one patient); the median number of submitted diagnoses was one. Two diagnoses were considered in seven patients, and five diagnoses were entertained in one patient.

Table 8 Clinical differential diagnosis of atrophic dermatofibroma
Full size table

Basal cell carcinoma was the most common diagnosis (18 patients); this represented 22.8% (23 of 79 submitted diagnoses) of the diagnoses suggested on the pathology requisition. The next most frequent diagnoses—each listed 14 times—were dermatofibroma and scar. Anetoderma and tumor cutis (each in five patients), nevus (in four patients), dermatofibrosarcoma protuberans (in three patients), and squamous cell carcinoma in situ, atrophoderma and morphea (each in two patients) were the other diagnoses suggested more than once.

The pathologic differential diagnosis of atrophic dermatofibroma included dermatofibrosarcoma protuberans in some of the patients. However, the use of immunohistochemical staining with factor XIIIa and CD34 aided in establishing the correct diagnosis. The atrophic dermatofibromas were usually factor XIIIa-positive and CD34-negative.

Pathogenesis

The etiology of dermatofibromas remains to be definitively established. Some investigators favor that dermatofibromas are a reactive process. About a fifth of the patients with cellular benign dermatofibromas have a history of trauma (such as an insect bite) or injection at the site of the lesion. However, most dermatofibromas develop spontaneously [4].

Other researchers suggest a neoplastic process for the development of dermatofibromas. Clonal markers—implying a monoclonal pattern—in the cells of dermatofibromas have been identified [4].

A heterogenous pathogenesis of dermatofibromas has also been entertained. This would include both a reactive process and a neoplastic process within the individual lesion. A fibroblastic proliferation of the fibrous portion would compose the reactive component, and a histiocytic proliferation would account for the neoplastic component [4].

The etiology of atrophic dermatofibromas may be similar to that of non-atrophic dermatofibromas. Both variants of dermatofibroma are more common in women. However, a history of trauma or injection is always absent in patients with atrophic dermatofibromas.

There is also a difference in lesion location. Cellular benign dermatofibromas most commonly occur on the legs. In contrast, atrophic dermatofibromas most frequently occur on the shoulder (25%), followed by the lower extremities (23%) and back (17%).

Treatment

An atrophic dermatofibroma is a benign vascular lesion. For some of the patients, the diagnosis was based on clinical features, and no intervention was performed [27]. In other individuals, including the men described in this paper, the residual lesion was observed after the biopsy [7, 24, 30]. However, the tumors were excised—either at the time of biopsy or subsequently—for many of the patients [7, 8, 17, 19,20,21, 26, 29]. Several of the investigators did not describe the management of the tumor [9, 15, 16, 27, 28].

Conclusions

An atrophic dermatofibroma is an uncommon benign variant of a dermatofibroma that has been reported in 102 patients. It is five times more common in women (53) than men (11); the gender was not provided for 38 individuals. It usually presents as an asymptomatic solitary patch on the shoulder of women aged 48 years and older; the central area is typically depressed. Other common sites include the lower extremity or back. White scar-like patches can be seen on dermoscopic examination; a patchy pigment network may also be present. The pathology of an atrophic dermatofibroma can show acanthosis, basal layer hyperpigmentation, and induction of basal cell carcinoma-like features, hair follicle formation or sebaceous hyperplasia in the epidermis; a proliferation of spindle-shaped fibroblasts is present in the dermis. Depression of the central surface and thinning of the dermis—in many cases, with at least 50 percent of dermal atrophy—can also be noted. Elastic fibers within the dermal tumor are either decreased or absent. The immunoperoxidase profile of an atrophic dermatofibroma is factor XIIIa-positive and CD34-negative. The pathogenesis of an atrophic dermatofibroma remains to be established. Although the diagnosis of an atrophic dermatofibroma may be suspected based on the clinical features of the lesion and the dermatoscopic findings, a biopsy of the lesion will confirm the diagnosis. If an excisional biopsy was performed, the tumor was removed at the time of diagnosis. Otherwise, the patient may elect to observe the residual lesion if the biopsy only includes part of the tumor; in this setting, periodic evaluation of the lesion site is a reasonable approach to the management of the residual tumor.