Giant pretibial cellular fibrous histiocytoma colliding with an epidermal cyst

Histiocytomas are common benign tumors of the skin. In contrast, giant histiocytomas are a rarity. We report a 43-year-old male patient, who presented with a 7 × 6 cm large firm tumor on his left lower leg. This was a long-standing lesion, but within the last three months, the tumor developed an exophytic nodule. A skin biopsy revealed an atypical spindle-cell tumor. We decided to perform a complete excision with a safety margin. Complete histopathological analysis confirmed the diagnosis of a collision tumor composed of a cellular fibrous histiocytoma and an epidermal cyst. The resulting defect was temporarily closed by vacuum-assisted closure before eventually a meshed split skin graft was transplanted. Proliferating fibrohistiocytic lesions should be surgically removed, and a careful histopathologic analysis is necessary to avoid delayed diagnosis of possible malignant lesions.