Fatally Metastatic Diagnostic Pitfall: Pseudolymphomatous Epithelioid Cutaneous Angiosarcoma Arising From an Ulcerative Scalp Injury.

Rare morphological variants of cutaneous angiosarcoma (AS) can be diagnostically challenging. Angiosarcoma located on the head and scalp of the elderly has been associated with especially poor prognosis. We report a difficult diagnostic pitfall of pseudolymphomatous AS variant with overlapping features of epithelioid variant and aberrant immunohistochemistry staining, arising on an ulcerative scalp lesion in a 79-year old woman. Initial histopathological exam showed extensive cutaneous necrosis with prominent dermal inflammation within which, scattered large cells were CD31 positive and CD34 negative. After cutaneous lymphoma was ruled out, these large cells within the inflammatory infiltrate were determined to be dermal histiocytes and initial biopsy was diagnosed as benign. Subsequent re-biopsy showed similar features and was also called benign. Post-mortem re-review found the large cells were positive for ERG and formed solid clusters and papillae in some areas. A diagnosis of pseudolymphomatous epithelioid AS was rendered. Autopsy demonstrated lung nodules to be metastatic AS, consistent with findings from scalp primary. Our case draws attention to multiple features that can confound angiosarcoma diagnosis, and we discuss the appropriate endothelial IHC panel to rule out angiosarcoma in this clinical context.