Dotted vessels appear as small red dots with a diameter of 0.01–0.02 mm, and they represent vessels aligned perpendicular to the skin surface .
Dotted vessels can be seen in inflamed skin, traumatized skin, or in skin overlying stasis. However, they can also be seen in cutaneous tumors. The presence of dotted vessels often implies that a lesion is melanocytic; in one study, 90% of the lesions with dotted vessels were melanocytic . In melanocytic tumors, dotted vessels confer a PPV of 38% for melanoma, 16% for dermal/congenital nevi, 21% for Clark nevi, and 16% for Spitz nevi. In benign nevi, dotted vessels correspond to vessels at the tips of the dermal papillae and dermoscopically often appear to be situated within the holes of the pigment network. In melanoma, dotted vessels, which are frequently found in conjunction with other vessel types, can be seen anywhere within the lesion but tend to be present at a higher concentration toward the center of the lesion . In a study of amelanotic and hypomelanotic melanomas (AHM), dotted vessels were more commonly seen in melanomas <1mm in thickness (27.6%) when compared with those >1 mm in thickness (20.0%); when evaluating purely amelanotic melanomas, dotted vessels were seen in 60% of cases . In another study, Bono and colleagues reported the presence of dotted vessels in 100% of thin amelanotic melanomas (<1mm) (n = 9) . The aforementioned data suggests that dotted vessels may be one of the first morphologic types of neoangiogenic vessels visible in melanoma because they appear to be more prevalent in thinner tumors.
In a study analyzing amelanotic/hypomelanotic benign melanocytic lesions (AHBML) and amelanotic/hypomelanotic nonmelanocytic lesions (AHNML) (tumors), dotted vessels were observed in 32.7% and 21.8% of lesions, respectively. In nonmelanocytic lesions, dotted vessels are commonly seen in psoriasis, clear cell acanthomas (CCA), and squamous cell carcinoma (SCC). The distribution and arrangement of dotted vessels within the aforementioned lesions can be very helpful in diagnosis. Dotted vessels in psoriasis are relatively uniform in size and are distributed homogenously throughout the plaque . When dotted vessels are arranged in a “string of pearls” or serpiginous distribution, then the diagnosis of CCA is almost certain. Dotted vessels present focally at the periphery or throughout the entire lesion and in association with adherent scale is suggestive of SCC .
Another more recently described vascular feature is the pattern of follicular red dots, which have been described in active discoid lupus erythematosus. The follicular red dots are seen surrounding the hair follicle openings and consist of regularly distributed, concentric reddish dots in a region of alopecia. This may represent dilation of blood vessels with extravasation of red blood cells surrounding the widened infundibula.
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