When the usual surprises

Abstract

A 20-year-old female patient, with no relevant personal or family history, presented with a tumorous lesion on her right upper extremity, which had been present for approximately three months and had experienced accelerated growth in the last month. Physical examination revealed a solitary, dome-shaped, erythematous-violaceous tumor, approximately 2 cm in diameter, with a smooth, firm, elastic surface, tender to palpation, and not adherent to deeper tissues, located on the lateral aspect of the right elbow. The patient denied any pre-existing lesions or history of local trauma. Dermatoscopy showed a central pink area with bright white lines and a peripheral pigmented network. The rest of the skin and mucous membranes were unaffected. Differential diagnoses included dermatofibroma, hemangioma, dermatofibrosarcoma protuberans, cutaneous lymphoma, and amelanotic melanoma. An excisional biopsy was performed for histopathological study and potential treatment. The biopsy revealed a preserved epidermis with an irregular central acanthotic area, dense spindle-shaped proliferation in the dermis with a fasciculated and whorled growth pattern, composed of cells with chromatic nuclei and acidophilic cytoplasm, and isolated histiocytoid-appearing cells. Scattered mitoses and central ectatic vessels with foci of hemorrhage were also present. Immunohistochemical analysis showed intense reactivity for CD10 with co-expression of vimentin and FXIIIa in the tumor cells, which were negative for CD34, CD31, alpha-actin, and S100. Blood vessels showed CD34- and CD31-positive endothelium. The Ki67 index was less than 5%.