Abstract

Dermatofibromas (DF), also known as fibrous histiocytomas, are benign dermal spindle cell proliferations of the skin. Histologically, DFs typically appear as a nodular dermal proliferation with spindle-shaped fibroblasts arranged in short intersecting fascicles with collagen entrapment at the lesion periphery. Unusual histological variants of DF can be challenging to diagnose. Herein, we present a case of sclerosing hemangioma, which histologically presented as a well-demarcated spindle cell proliferation admixed with dilated blood vessels and diagnosed with immunohistochemistry (IHC) studies. A 68-year-old female presented to outpatient clinic with a lesion of concern on her leg that had been growing for the past year. Clinically, the patient had a well demarcated, round 4 mm skin colored to erythematous papule on the posterior left leg. Histologic examination revealed a nodular lesion composed of fibrocytes and histiocytes with coarse collagen bundles with numerous admixed blood vessels. Considering the location, patient age, and the histological features of the lesion, differential diagnoses included Kaposi sarcoma, spindle cell hemangioma and angiosarcoma. IHC studies showed diffuse Factor 13a positivity with CD34, CD68, Melan-A, SOX-10, desmin and CKHMW negativity. The lesion was diagnosed as DF, sclerosing hemangioma subtype and no further treatment was needed. While typical variants of DF are easy to diagnose both clinically and on histopathology, less common variants exist. Based on clinical and histopathological findings, rarer variants of dermatofibromas can have features in common with malignant or vascular tumors, thus it is important to be able to recognize these rare variants.

Financial Disclosure:
The poster abstract presenter listed below disclosed the following information about their financial interests. The ASDP Ethics Committee has reviewed these disclosures and determined that no conflicts of interest exist between financial relationships and educational content being presented.

Speaker	Company	Affiliation/Relationship
Babar Rao, MD	Caliber Imaging & Diagnostics	Consultant