Rare mimic of angiosarcoma: Erythema ab igne with reactive angiomatosis

Abstract

Erythema ab igne is an uncommon physical dermatosis that presents with localized patches of reticulated erythema and hyperpigmentation corresponding with the underlying dermal venous plexus. The rash occurs in response to chronic heat exposure that does not meet the threshold for thermal burn of the skin. The histopathologic findings are characterized by atrophy and thinning of the epidermis, focal hyperkeratosis, and keratinocyte atypia. The dermis displays dilated capillaries, evidence of pigment incontinence, and prominent elastotic material. We report a case of a 65‐year‐old male who presented to his primary care physician with a 1‐year history of reticular erythema and hyperpigmentation with focal ulceration on his right lateral leg. Histopathology on biopsy revealed mild hyperkeratosis and focal epidermal atrophy; however, the most striking finding was a proliferation of dermal vascular spaces lined by pleomorphic endothelial cells and numerous mitotic figures, which was morphologically compatible with angiosarcoma. However, clinicopathologic correlation and immunostaining revealed an actual diagnosis of erythema ab igne with reactive angiomatosis. Reactive angiomatosis—morphologically mimicking angiosarcoma—is a rarely reported feature of severe erythema ab igne, and dermatopathologists should be aware of this possibility to avoid misdiagnosis of erythema ab igne as angiosarcoma.

Bullous Erythema ab Igne Unexpected Biopsy: Answer

“…Reactive angiomatosis occurring in EAI causing endothelial cell atypia has been reported within biopsy specimens of EAI in only 4 previous reports. 4,6–8 In the case presented here, although there was initial concern on histopathologic review for a malignant vascular neoplasm such as angiosarcoma, the discrepancy between the clinical description and histopathologic findings prompted the dermatopathologist to review the patient's history and clinical photographs in detail, for clinicopathologic correlation. Reactive angiomatosis, instead of a true vascular neoplasm, was then confirmed and supported by appropriate immunohistochemistry stains (positive CD31 and CD34).…”

“…5 The superficial nature of the vessels in EAI can be used as a clue to help distinguish this entity from cutaneous angiosarcoma. 6 In the setting of EAI, the atypical proliferation of endothelial cells is believed to result from damage secondary to chronic, long-standing heat exposure.…”