DERMATOFIBROMA

Dermatofibroma, also known as benign fibrous histiocytoma, is an area of focal dermal fibrosis and one of the most common skin neoplasms. It is a mesenchymal cell lesion of the dermis that appears as a firm subcutaneous papule or small nodule. Dermatofibromas can occur anywhere on the body, but are most commonly seen on the extremities, particularly the legs. They are usually solitary lesions that are most common in young adults, and they may or may not be associated with overlying skin changes.^1-4

Pathophysiology

• The pathophysiological mechanism underlying the development of dermatofibroma is unknown and remains and a controversial topic.^1,3,4
• The two leading theories propose that dermatofibroma may be due to either a reactive process or neoplastic process, and there is evidence available to support both theories.
  • According to the reactive process theory, a history of inciting local trauma (eg, a shaving accident or insect bite) may result in an exuberant healing response with a proliferation of fibroblasts and subsequent fibrosis; however, in most patients there is no inciting trauma and the lesion develops spontaneously.
  • Evidence for a neoplastic process is demonstrated by the clonal proliferative growth of dermatofibroma.^1,3,4

Related Anatomy

• Dermis
• Epidermis
• Fibroblasts
• Histiocytes
• Collagen

Incidence and Related Conditions

• Dermatofibromas are one of the most common skin tumors. Their overall incidence is difficult to estimate since most patients are asymptomatic, but in one study, they accounted for ~3% of all dermatopathology laboratory specimens.^2,4
• Dermatofibromas can occur at any age, but are most commonly reported between ages 20-49. They are more common in women than men, with a female-to-male ratio of 2:1 or higher.^1,4
• Dermatofibrosarcoma protuberans
• Fibroma durum
• Fibroxanthoma
• Sclerosing hemangioma
• Subepidermal fibrosis

Differential Diagnosis

• Dermatofibrosarcoma protuberans
  • It is extremely important to distinguish dermatofibromas from dermatofibrosarcoma protuberans, an aggressive cutaneous malignancy.⁴ In contrast to dermatofibroma, DFSPs enlarge rapidly, are very firm to the touch, and are malignant neoplasms.
• Basal cell carcinoma
• Blue nevus
• Cutaneous chondroma
• Desmoplastic trichoepithelioma
• Epithelioid sarcoma
• Foreign body granuloma
• Giant cell tumor
• Granular cell tumor
• Kaposi sarcoma
• Lichenoid keratosis
• Melanoyctic nevus
• Melanoma
• Neurothekeoma
• Nodular fasciitis
• Prurigo nodularis
• Squamous cell carcinoma

A typical patient is a 26-year-old woman without any history of recent trauma. About one month ago, she observed a solitary nodule gradually developing on the left lateral upper arm. The lesion was dark brown and circular, measured ~1.5 cm in diameter, and was firm to the touch. She did not experience any additional symptoms, but nonetheless consulted with a dermatologist to be evaluated.

• Infection
• Bleeding
• Scarring
• Local recurrence
• Distant metastases

• Surgical excision is generally associated with an excellent prognosis, but may lead to scarring.⁴
• Cryotherapy and intralesional injections are variably effective and may not produce optimal cosmetic outcomes.³

• Papule or small nodule
  • Size ranges from 2mm to 2 cm in diameter
  • Shape is round or ovoid, with a well-defined border
  • Color is variable and includes brown, dark brown, yellow, pink, blue, red, brownish red, and black
  • Lesions have either a shiny or keratotic surface texture
  • On palpation, the tumor is firm and feels as if a small button or pea is attached to the skin surface
  • More frequently indurated than elevated
  • Usually occur in isolation
• A dermatofibroma is often easy to diagnose clinically when it presents in its classical form (ie, a small, raised, cutaneous nodule with a red-brown surface), but the diagnosis becomes difficult in variants and atypical cases.²
• Patients should be educated that dermatofibromas are benign and do not necessarily require excision. 
• One clinical clue to differentiate dermatofibromas from other tumors is the presence of the “dimple” sign: when compressed from the sides, the center dimples. Most dermatofibromas exhibit this sign and it is rarely seen in any other skin lesions.^1,3
• Pathologic review of the lesion may be needed to rule out malignancy or if there is any doubt of the diagnosis.
  • Histopathologically, these lesions are characterized by a localized proliferation of spindle-shaped fibrous cells admixed with histiocytoid cells within the dermis.^1,4
• Dermatoscopy is another workup option that most commonly reveals a central white patch with a peripheral pigmented network.⁴

New and Cited Articles

1. Marks JG, Miller JJ. Lookingbill and Marks’ Principles of Dermatology. Fifth Ed. London, New York: Saunders Elsevier; 2013.
2. Kelati A, Aqil N, Baybay H, Gallouj S, Mernissi FZ. Beyond classic dermoscopic patterns of dermatofibromas: a prospective research study. J Med Case Rep 2017;11(1):266. PMID: 28927449
3. Wang SQ, Lee PK. Treatment of dermatofibroma with a 600 nm pulsed dye laser. Dermatol Surg 2006;32(4):532-535.PMID: 16681661
4. Myers DJ, Fillman EP. Dermatofibroma. In: StatPearls.Treasure Island (FL) 2019.PMID: 29262213

Reviews

1. Gershtenson PC, Krunic AL, Chen HM. Multiple clustered dermatofibroma: case report and review of the literature. J Cutan Pathol2010;37(9):e42-5. PMID: 19614987
2. Lehmer LM, Ragsdale BD. Digital dermatofibromas--common lesion, uncommon location: a series of 26 cases and review of the literature. Dermatol Online J2011;17(8):2. PMID: 21906482