Can dermatofibromas (benign skin growths) become depressed instead of firm?

Can Dermatofibromas Become Depressed Instead of Firm?

Yes, dermatofibromas can present as depressed or atrophic lesions rather than the typical firm nodules, which is known as atrophic dermatofibroma, a distinct clinical variant.

Atrophic Dermatofibroma: A Unique Variant

Atrophic dermatofibromas represent an uncommon but well-documented variant of dermatofibromas that present with different clinical characteristics compared to the classic form:

Clinical Characteristics

• Appearance: Present as flat or depressed macules rather than firm nodules 1
• Color: Can range from brown to white to red 1
• Location: Unlike classic dermatofibromas that typically occur on the legs, atrophic variants tend to occur on the upper back and arms 1
• Definition: Characterized by dermal atrophy of more than 50% of the lesion 2

Pathologic Features

• Epidermal acanthosis
• Basilar hyperpigmentation
• Fibroblast hyperplasia
• Decreased or absent elastic fibers within the lesion 1

Pathogenesis of Atrophic Presentation

The pathogenesis of atrophic dermatofibromas is not fully understood, but several mechanisms have been proposed:

• Loss of elastic fibers: This appears to play a key role in the development of the characteristic atrophic appearance 1
• Dermal depression: Some researchers suggest that the thinning of the dermis compared to adjacent non-lesional skin results from depression rather than true tissue atrophy 3
• Terminology debate: Some authors have suggested "delled dermatofibroma" as a more appropriate term than "atrophic dermatofibroma" because the appearance results from depression rather than true tissue loss 3

Differential Diagnosis

When encountering a depressed skin lesion that might be an atrophic dermatofibroma, it's important to distinguish it from:

1. Dermatofibrosarcoma protuberans (DFSP)
2. Other atrophic skin conditions
3. Morphea
4. Anetoderma

Diagnostic Approach

Due to the atypical presentation, a biopsy is often required for definitive diagnosis:

• Punch or incisional biopsy that samples the subcutaneous layer is strongly recommended 4
• Immunohistochemical staining may be needed to differentiate from other entities:
  • CD34 (typically positive in DFSP, variable in dermatofibroma)
  • Factor XIIIa (typically positive in dermatofibroma, negative in DFSP) 4

Clinical Significance

Understanding that dermatofibromas can present as depressed lesions is important because:

1. It prevents misdiagnosis and unnecessary aggressive treatment
2. It helps differentiate from more concerning entities like DFSP
3. It allows appropriate management of symptomatic lesions

Management Considerations

For symptomatic atrophic dermatofibromas:

• Observation is appropriate for asymptomatic lesions
• Surgical excision if symptomatic or for cosmetic concerns
• Alternative treatments like fractionated CO2 laser combined with topical corticosteroids have been reported for symptomatic cases 5

Unlike DFSP, which requires wide surgical margins due to its infiltrative growth pattern and potential for local recurrence 4, atrophic dermatofibromas generally have benign behavior and don't require extensive excision.