Pseudoangiosarcomatous squamous cell carcinoma: report of a rare and challenging clinical and pathologic diagnosis

An 86-year-old man presented with a scaly papule of his left preauricular cheek. Initial biopsy was non- diagnostic; repeat biopsy showed acanthosis and mildly atypical cells in a configuration reminiscent of vascular lumens. Immunostaining was positive for ERG and p53, leading to a working diagnosis of cutaneous angiosarcoma. MRI face and neck with contrast did not show evidence of invasive or metastatic disease. A moat procedure was performed with two-centimeter margins and en face sectioning to define peripheral margins, which were clear. A debulk specimen was simultaneously obtained, which revealed deeply invasive, monomorphous cords of cells recapitulating the appearance of vascular networks. Given clinical-pathological discordance and deep extension of the tumor, an extensive staining workup was performed. The specimen was uniformly positive for high molecular weight keratin (HMWK) 903, keratin cocktail (AE1/AE3, Cam 5.2), and ERG, but negative for CD31, leading to a diagnosis of pseudoangiosarcomatous SCC (PA-SCC). The lesion was definitively excised with delayed repair after confirmation of clear deep margins. PA-SCC is a rare, highly aggressive variant of SCC that may mimic angiosarcoma clinically, histologically, and even immunophenotypically [1], as seen here. The tumor’s expression of ERG, a highly specific endothelial marker, complicated the distinction between angiosarcoma and PA-SCC. To our knowledge, only one case of PA-SCC with aberrant ERG expression has been reported [2]. Recognition of PA-SCC, especially subtypes with aberrant endothelial marker expression, is of vital importance to guide appropriate treatment and subsequent monitoring, given the tumor’s aggressive nature and high associated mortality [3].