This is an example of primary angiosarcoma of breast, status-post neoadjacent therapy (which is why there is a significant amount of tumor necrosis).
Keys to the diagnosis of this well-differentiated example include neoplastic vessels widely infiltrating soft tissue. Cytologic atypia is relatively mild, and multilayering of neoplastic endothelial cells is present. In contrast, vasoformation can be scarce in poorly differentiated and epithelioid examples, instead consisting of solid growth of markedly atypical cells.
In addition, there is variable loss of vascular markers. ERG is usually the most sensitive marker, but a panel of immunohistochemical stains is recommended, since even rare ERG-negative examples have been reported (such as a case posted by Dr. Jerad Gardner: https://kikoxp.com/posts/21794)
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Keys to the diagnosis of this well-differentiated example include neoplastic vessels widely infiltrating soft tissue. Cytologic atypia is relatively mild, and multilayering of neoplastic endothelial cells is present. In contrast, vasoformation can be scarce in poorly differentiated and epithelioid examples, instead consisting of solid growth of markedly atypical cells.
In addition, there is variable loss of vascular markers. ERG is usually the most sensitive marker, but a panel of immunohistochemical stains is recommended, since even rare ERG-negative examples have been reported (such as a case posted by Dr. Jerad Gardner: https://kikoxp.com/posts/21794)
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Want more cases?
Check out my pathology #MEGAIndex, which contains links to ALL my posts & videos!
You can also follow me on Twitter, Instagram, Facebook, YouTube, and Mastodon!