Abstract

A 64-year-old man presented with a soft subcutaneous nodule of the left vertex scalp. Fifteen years prior, he had a cystic lesion at the same site excised and called benign, but further pathologic information about this original lesion is unavailable. The subcutaneous cyst-like nodule had subsequently recurred and was becoming symptomatic.  He had no documented history of radiation therapy to the scalp. Excisional biopsy was performed. Histopathologic examination of the excision specimen demonstrated a relatively well-circumscribed subcutaneous nodule composed of acantholytic epithelioid cells with enlarged, hyperchromatic nuclei growing in an infiltrative, pseudovascular pattern as well as mature fat. This histopathologic appearance raised concern for primary angiosarcoma, but the neoplastic cells were surprisingly not immunoreactive to ERG, CD34, CD31, and FLI-1. Instead, they exhibited strong positivity for keratin AE1/AE3, p63, and p40, consistent with a diagnosis of pseudovascular squamous cell carcinoma.  The medical literature contains roughly 30 total cases of this entity arising in skin. Because of this rarity, the prognostic significance of this histologic pattern is currently unclear. Interestingly, two other cases have been reported in association with prior trauma including a burn wound and decubitus ulcers. To our knowledge this is the first reported case arising at a site of prior skin excision. The differential diagnosis of infiltrative “angiosarcoma-like” growth pattern should include pseudovascular squamous cell carcinoma.