Atrophic Dermatofibroma: A Rare Variant With Distinct Clinical and Histopathological Features.

Dermatofibroma (DF) is a common benign cutaneous soft-tissue tumor that typically affects females between the third and fifth decades of life. While its pathogenesis is not fully understood, DF has been associated with minor local trauma and insect bites. We present a case of atrophic DF in a 35-year-old Saudi female who noticed a solitary, hyperpigmented, depressed plaque on her back that had been present for five years. The lesion initially appeared as a small papule but gradually increased in size while remaining asymptomatic, without pain, itching, or systemic complaints. Physical examination revealed a well-demarcated, hyperpigmented, depressed plaque without ulceration or surrounding erythema. Histopathological examination supported the diagnosis of atrophic DF, and immunohistochemical staining showed focal positivity for Factor XIIIa and negative staining for CD34, S100, HMB45, and p63. Atrophic DF is a rare variant characterized by a depressed clinical appearance and distinctive histopathological features that may create diagnostic challenges. Recognition of this uncommon presentation and correlation of the clinical, histopathological, and immunohistochemical findings can help distinguish it from other atrophic and spindle-cell cutaneous lesions.