Abstract

A 77-year-old male with past medical history of multiple non-melanoma skin cancer lesions presented to his dermatologist for routine follow-up. On physical examination, a new lesion was noted on the patient’s right temple adjacent to the hairline. Initially, the dermatologist was concerned for a non-melanoma skin cancer, prompting the lesion to be excised via a simple shave biopsy which was subsequently sent to pathology for examination. Histologic examination of H&E stained sections showed skin with diffuse background sun-damage and a large, partially-circumscribed dermal proliferation of markedly atypical spindled to epithelioid cells. Numerous mitotic figures were noted within the dermal proliferation. Conspicuous pseudo-vascular spaces were noted throughout the lesion. Additionally, there were patchy areas of red cell extravasation and hemosiderin deposition.

Following morphologic examination, immunohistochemistry was performed to evaluate the pseudo-vascular spaces. ERG showed patchy weak expression within a subset of lesional cells. FLI1 demonstrated weak cytoplasmic uptake, however, there was no definitive nuclear staining in lesional cells. Neither ERG or FLI1 highlighted a definitive vasoformative pattern. The cells of interest were also negative for CD34, CD31, Mart-1, SOX-10, desmin, smooth muscle actin, a pancytokeratin cocktail, and p40. Overall, the combination of histomorphology and immunoprofile was most compatible with an atypical fibroxanthoma/pleomorphic dermal sarcoma with pseudoangiomatous features. A recommendation was made to completely excise the lesion. This case highlights the importance in considering differentials when rendering a diagnosis of AFX/PDS. The pseudoangiomatous pattern encountered in this case further confirms the significance of ruling out other potential aggressive diseases including cutaneous angiosarcoma.