Which diagnosis is characterized by brown, firm papules on the legs that may arise after trauma due to fibroblast overgrowth?

• A. Dermatofibroma
• B. Epidermal inclusion cyst
• C. Lipoma
• D. Pilar cysts

Answer: (A)

Minor skin trauma can trigger a fibrous reaction in the dermis that leads to a dermatofibroma—an overgrowth of fibroblasts and histiocytes forming a small, brown to tan, firm papule most often on the legs after injury. These lesions are benign and classically have a firm, indurated feel; often you can see a dimple sign when the lesion is squeezed laterally, reflecting its dermal tethering. This explains the described presentation: a pigmented, firm papule on the legs arising after trauma due to fibroblast proliferation.

Epidermal inclusion cysts are keratin-filled sacs with a central punctum and are usually not pigmented or strictly trauma-related. Lipomas are soft, subcutaneous, and mobile. Pilar cysts occur on the scalp and arise from hair follicle epithelium.