The Tail and the String Sign: New Sonographic Features of Subcutaneous Melanoma Metastasis

No highly specific sonographic imaging findings to evaluate melanoma spread along the lymphatic vessels have ever been described. Between January 2009 and December 2012, a consecutive group of 531 melanoma patients at their initial stage or during follow-up for nodal or extra-nodal superficial metastasis were evaluated retrospectively to assess the presence of two sonographic findings demonstrating superficial lymphatic metastasis: a "tail" sign (a thin hypoechoic prolongation from one or both poles of a superficial metastasis) and a "string" sign (multiple in-transit lesions connected to each other in a rosary image). The total number of superficial metastatic lesions was 222. The tail sign was seen in 13 of the 222 lesions (5.9%). The string sign was detected in four patients (4.5%). These signs showed a low sensitivity with a very high specificity (100%). Tail and string signs may represent an additional finding of high specificity to be employed in the differential diagnosis of melanoma patients.