Preoperative ultrasonographic identification of the sentinel lymph node in patients with malignant melanoma.

Abstract

Dissection of the "sentinel lymph node" (SLN) as identified by lymphoscintigraphy is becoming increasingly important in the treatment of patients with malignant melanoma. The purpose of the current study was to determine whether the SLN also could be identified by ultrasound. Sixty-seven patients with malignant melanoma (40 females and 27 males, with an average age of 48.8 years) in whom extirpation of the SLN was indicated underwent ultrasonography of the regional lymph nodes prior to preoperative lymphoscintigraphy. The location of the melanoma was the legs in 30 patients, the arms in 14 patients, and the trunk in 23 patients. During regional ultrasonography, the location of the lymph nodes that differed in the cortex/medulla ratio from the surrounding lymph nodes was marked on the skin corresponding to the planes of insonation (M1) when the probe was held vertically to the skin surface. After lymphoscintigraphy using technetium-99m, the position of a gamma probe at which the highest count rate vertical to the skin surface was recorded also was marked (M2). In the inguinal region, the agreement between M1 and M2 was found to be 100% (40 of 40 SLNs) and was 72.5% in the axilla (29 of 40 SLNs). In patients with melanomas located on the leg, the location of M1 and M2 agreed in 97% of cases (36 of 37 lymph nodes in 30 patients); in patients with melanomas located on the arms, the agreement was 76% (13 of 17 lymph nodes in 14 patients) and in patients with melanomas located on the trunk, the agreement was 75% (21 of 28 lymph nodes in 23 patients). The position documented by ultrasound relative to the neighboring structures of the SLN was confirmed intraoperatively in all cases. The results of the current study indicate that the SLN in patients with melanoma located on the limbs, especially the legs, are characterized by a specific sonomorphologic pattern. Preoperative sonography might constitute an important addition to lymphoscintigraphy in the planning of SLN biopsy.