What is Dermatofibroma?
Dermatofibromas are benign, noncancerous lesions of the skin. They are elevations caused by cell overgrowth from the second layer of the skin, called the dermis. Such growths can appear as nodular elevations (single or multiple) and can be coloured anywhere from dark pink/salmon hue to brown or black, although they are often described as reddish-brown. They are usually firm to the touch, with smooth or regular, rounded edges [1, 2].
Dermatofibromas are usually less than 1cm across, and they grow slowly. They can appear anywhere on the body but are common on the lower legs and upper arms. Dermatofibromas are firm, rubbery lumps that are benign and painless (though they might itch or hurt occasionally) [2]. They can be similar to ganglion cysts.
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What are the causes of Dermatofibroma?
Although the exact mechanism is not well understood, Dermatofibromas often arise following some type of previous trauma to the skin, including punctures from splinters, insect bites or other small injuries. Based on this regular observation, some have suggested that trauma could represent a causative mechanism for Dermatofibroma [1, 2, 3, 4].
Aside from minor skin trauma, older age is another risk factor since Dermatofibromas have a higher frequency in adults aged 20 to 49 more frequently in women than men. People with an impaired immune system may also be at increased risk of developing Dermatofibromas [1].
What is Nodular Melanoma?
Nodular Melanoma is a kind of skin cancer. It grows from the skin’s melanocyte cells. Melanocytes are the cells that produce and release melanin, the brown-to-black pigment that gives colour to your skin. Nodular Melanoma grows very quickly and is also often very firm to the touch. It’s the second most common Melanoma, being diagnosed between 15% and 30% of the time [5, 6, 7].
What are the causes of Nodular Melanoma?
Nodular Melanoma starts with melanocyte skin cells that have undergone mutation to become cancerous. The cells probably acquired the mutation after exposure to ultraviolet (UV) radiation from the sun lasers or artificial tanning beds. Too much UV radiation in a person’s skin can damage the cellular DNA leading to mutations that cause cells to grow out of control [8].
Although the aetiology of Nodular Melanoma remains somewhat a mystery, genetic and environmental risk factors both play a role in the development of this kind of cancer. For example, clearly connective tissue genomic mutations are associated with increased risks of melanoma but not specifically with nodular melanoma [9].
Dermatofibroma and Nodular Melanoma
Differences
Commonly confused with each other: Dermatofibroma and Nodular Melanoma. Although the pathogenesis of these two skin lesions differs greatly, their clinical presentation can pose a challenge when attempting to distinguish one from the other. Dermatofibroma is a benign fibrohistiocytic tumor, representing a mixture of fibroblastic and histiocytic cells, commonly presenting as a firm, subcutaneous, solitary, dome-shaped nodule most prevalent on the extremities [10, 11]. Conversely, Nodular Melanoma denotes a rising incidence of an often aggressive malignancy, characterized by scattered, atypical melanocytes in dermal and epidermal layers, ultimately producing melanin [12].
Among the differences, proliferation activity is the main one, since a MIB-1 staining with a high proliferative index allows us to rule out this diagnosis (DM) as it is beneficial to differentiate this entity from a malignant one, such as Nodular Melanoma [10].
However, the normal Dermatofibroma is also considered benign and less likely to metastasize while the Nodular Melanoma is always malignant and more prone to metastasis [12, 13].
Similarities
As for the differences, despite their distinct underlying causes, lesions of these two entities might look alike from the beginning. They can both appear as a single, firm pigmented nodule and be difficult or impossible to distinguish clinically [14]. Hemosiderotic Dermatofibroma, a rare variant of Dermatofibroma, can be clinically indistinguishable from Melanoma, with a tendency to undergo bleeding [14]. Likewise, Dermatofibromas can mimic features of Melanoma (16.2% of cases) [14, 15].
Conclusion
In conclusion, Dermatofibroma and Nodular Melanoma present similar clinical symptoms. However, they are different in the aspect that Dermatofibroma is a benign growth whereas Nodular Melanoma is a malignant lesion. Any suspicious skin lesions should be consulted with a healthcare professional to have them examined and treated.
