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A 41-year-old man presents for evaluation and removal of a growth on his right forearm. The lesion has been present for at least 1 year and is at times painful. The patient denies antecedent trauma that may have caused the growth. He is in good health, takes no medications, and has never smoked. Physical examination reveals a 1.2- cm firm nodule with a whitened center and slightly erythematous border. Palpation of the growth elicits tenderness. There are no similar lesions noted elsewhere on the body and palpation of the axillary lymph nodes are normal.
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Dermatofibromas (DFs), also known as fibrous histiocytomas, are common benign tumors that most frequently arise on the lower extremities of women.1 According to Han et al, the highest frequency of tumor occur in patients between 20 and 29 years of age.1 Lesions are round to ovoid in shape and range in size from 0.3 cm to more than 1.0 cm and are usually dome-shaped in appearance. Coloration may be either flesh-toned, pink, or hyperpigmented.1
Many lesions will dimple upon lateral compression, known as Fitzpatrick sign, which was once thought to be pathognomonic for DFs.2 Although most lesions are asymptomatic, DFs are at times painful.3 The cause of DF is unknown; a reactive process to minor trauma such as an insect bite has been postulated.1
Diagnosis of DF is confirmed by histopathology, which reveals a dermal tumor comprised of whorling fascicles of spindle-shaped cells within a collagen matrix.1 A number of histopathologic variants have been described such as hemosiderotic, cellular, epithelioid, clear cell, balloon cell, and signet-ring cell.4 The most common dermatoscopic finding is that of a central whitened core with a delicate pigment network at the periphery.5
Full excision is curative but may result in an unacceptable scar and is often discouraged unless the DF is symptomatic or is repeatedly traumatized.
Stephen Schleicher, MD, is director of the DermDox Center for Dermatology in Pennsylvania, as well as associate professor of medicine at Commonwealth Medical College and clinical instructor of dermatology at Arcadia University and Kings College.
References
1. Han TY, Chang HS, Lee JH, Lee WM, Son SJ. A clinical and histopathological study of 122 cases of dermatofibroma (benign fibrous histiocytoma). Ann Dermatol. 2011;23(2):185-192. doi:10.5021/ad.2011.23.2.185
2. Meffert JJ, Peake MF, Wilde JL. ‘Dimpling’ is not unique to dermatofibromas. Dermatology. 1997;195(4):384-386. doi:10.1159/000245994
3. Cohen PR, Erickson CP, Calame A. Painful tumors of the skin: “CALM HOG FLED PEN AND GETS BACK”. Clin Cosmet Investig Dermatol. 2019;12:123-132. doi:10.2147/CCID.S216860
4. Alves JVP, Matos DM, Barreiros HF, Bartolo EAFLF. Variants of dermatofibroma—a histopathological study. An Bras Dermatol. 2014;89(3):472-477. doi:10.1590/abd1806-4841.20142629
5. Camara MF, Pinheiro PMR, Jales RD, da Trindade Neto PB, Costa JB, de Sousa VLLR. Multiple dermatofibromas: dermoscopic patterns. Indian J Dermatol. 2013;58(3):243. doi:10.4103/0019-5154.110862
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