Unveiling the Atrophic Dermatofibroma: A Rare Dermatological Entity

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Atrophic dermatofibroma, a distinctive form of dermatofibroma, is a benign fibrohistiocytic lesion that is often underdiagnosed due to its atypical presentation. This variant is characterized by a clinically flat or atrophic surface with a tendency to depress upon touch. Histopathologically, it is identified by a significant reduction in the dermal thickness and elastic fibers, setting it apart from the more common forms of dermatofibroma.

Clinical Presentation and Case Report

A 57-year-old female presented with well-defined, firm, brown macules on her left flank, measuring 3x2 cm with an atrophic surface. The lesion, initially noticed a decade ago, was associated with mild itching but no history of trauma or injection. Upon examination, a central depression was evident post-compression, a telltale sign of atrophic dermatofibroma.

Discussion on Dermatofibroma Variants

Dermatofibromas typically present as firm, hyperpigmented, and asymptomatic papules, most frequently on the lower limbs. They exhibit a 'dimple sign' upon compression, a key diagnostic feature. The atrophic variant, however, is less common, accounting for about 2% of all dermatofibromas, and is particularly found on the upper trunk of women, with an average age of onset at 49.7 years.

Dermoscopy is instrumental in evaluating pigmented lesions, revealing a central plate and a fine, regular pigmented network at the periphery, indicative of a non-melanocytic lesion. Dermatofibromas are dermal proliferations of spindle cells, a mixture of fibroblasts, collagen, histiocytes, and blood vessels, with various cytological presentations, including spindle to oval-shaped cells and foamy or hemosiderin-laden cells.

The etiology of dermatofibroma is believed to involve a series of inflammatory responses following trauma, leading to granulation tissue, granulomatous inflammation, and fibrosis. Elastophagocytosis, the phagocytosis of elastic fibers by tumor cells, has been implicated in the atrophic variant, as has the inhibition of platelet-derived growth factor beta (PDGFB) receptor, potentially altering the stroma composition.

Histopathological Examination and Differential Diagnosis

Histopathologically, atrophic dermatofibroma is distinguished by a reduction of at least 50% in dermal thickness and elastic fibers, confirmed by specific staining techniques. Immunohistochemical examination shows positivity for factor XIIIa and negativity for CD34, differentiating it from atrophic dermatofibrosarcoma protuberans.

Differential diagnoses for atrophic dermatofibroma include a range of conditions such as atrophic dermatofibrosarcoma protuberans, anetodermia, atrophic scarring, and other sclerotic or atrophic skin lesions. Given the propensity for misdiagnosis, it is imperative to consider atrophic dermatofibroma in the presence of atrophic or sclerotic lesions, particularly in middle-aged women with lesions on the upper trunk.

The atrophic variant of dermatofibroma, while infrequent, requires careful consideration in the dermatological evaluation of atrophic lesions. Recognizing this variant is essential for accurate diagnosis and appropriate management, avoiding potential misdiagnosis and ensuring optimal patient care.

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