Track

Case Reports

Abstract

Dermatofibroma or fibrous histiocytomas (FH) are common skin tumors. These lesions are typically small and range between 0.5 to 2 cm in size.  Lesions larger than 5 cm are considered giant dermatofibromas. Aneurysmal and hemosiderotic variants are described by prominent hemosiderin pigment. Giant hemosiderotic and aneurysmal dermatofibromas are extremely rare, and only a handful of cases have been reported to date. A 38-year-old male presented with a slowly enlarging, lobulated, cystic scalp lesion of approximately 20-years following trauma. He underwent an incisional biopsy and subsequent wide local excision with skin substitute reconstruction. The multilobular mass measured 18.5x9.0x4.6 cm, demonstrating areas of skin ulceration and a fleshy cut surface. Histologically, the lesion was comprised of dermal spindled, histiocytic cells in a storiform pattern with abundant small intervening vessels, blood-filled spaces devoid of endothelial lining, ample hemosiderin deposition, and occasional mitotic figures. Immunohistochemistry showed characteristic Factor XIIIa reactivity and an uncharacteristic patchy immunoreactivity for CD34 in a hypercellular region of the resection  Next-generation sequencing evaluation of 138 genes was negative for somatic gene fusions or common BCORTandem duplications. To our knowledge, this is the largest giant aneurysmal FH currently described in the literature. The unusual clinical presentation and histologic variance may pose challenging clinicopathologic differentials, including benign and malignant vascular and pigmented lesions, angiomatoid malignant FH, dermatofibrosarcoma protuberans, and other cutaneous and soft tissue sarcomas. To increase the awareness of these unusual tumors, we review the histologic and radiologic findings and theories behind their etiology.