Extravascular migratory metastasis is a form of cancer metastasis in which tumor cells spread by tracking along the abluminal aspect of vessel walls without breaking the vascular endothelial lining or intraluminal invasion. This phenomenon has been extensively described in melanoma and is being increasingly recognized in other neoplasms. Various modalities of treatment, including radiation-, chemo-, targeted-, and immune- therapies may potentially induce angiotropic behavior in neoplastic cells. Although there is a risk for tumor recurrence and metastasis, angiotropism may be under-recognized and is rarely reported. Here, we report a case of recurrent poorly-differentiated acantholytic squamous cell carcinoma of the scalp with extensive perineural invasion, previously treated with multiple therapies. There was multifocal extravascular cuffing of neoplastic cells around and focally involving the walls of small to medium-caliber blood vessels within and surrounding the tumor, without obvious tumor intravasation. In addition, small subtle nests of neoplastic keratinocytes were noted along the abluminal aspect of a large-caliber deep dermal blood vessel in an en-face margin, away from the main tumor mass. Such involvement can be difficult to identify; and thus, may be missed particularly during intra-operative frozen section evaluation, leading to false-negative margins and is therefore, a diagnostic pitfall.
Keywords: angiotropism; recurrence; squamous cell carcinoma.
© 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.