Polymorphous vessels are used to describe the vasculature of lesions in which two or more types of vessel morphologies are detected.
The presence of polymorphous vessels may suggest a diagnosis of melanoma. The most common combination of vessel types seen in melanoma is the presence of both dotted vessels and linear–irregular vessels. In a study of lesions with vascular features seen on dermoscopy, only 20% of the lesions contained polymorphous structures, which correlated with a PPV of 52.6% for melanoma. More specifically, the combination of dotted and linear–irregular vessels was found in 18% of amelanotic/hypomelanotic melanomas but only extremely rarely in other nonmelanoma amelanotic/hypomelanotic lesions (1.8% of AHNML and 0% of AHBML). Polymorphous vessels in combinations other than dotted vessels and linear–irregular vessels may be observed in cutaneous melanoma metastases. They can also be seen in papillomatous melanocytic nevi and other tumors, such as eccrine poromas.
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