Sentinel lymph node detection using methylene blue in patients with early stage cervical cancer

To evaluate the feasibility of sentinel lymph node (SLN) detection in patients with cervical cancer using the low-cost methylene blue dye and to optimize the application procedure.

Patients with stage Ib(1)-IIa cervical cancer and subjected to abdominal radical abdominal hysterectomy and pelvic lymphadenectomy were enrolled. Methylene blue, 2-4 ml, was injected into the cervical peritumoral area in 77 cases (4 ml patent blue in the other four cases) 10-360 min before the incision, and surgically removed lymph nodes were examined for the blue lymph nodes that were considered as SLNs.

High SLN detection rate was successfully achieved when 4 ml of methylene blue was applied (93.9%, 46/49). Bilaterally SLN detection rate was significantly higher (78.1% vs. 47.1% P=0.027) in cases when the timing of application was more than 60 min before surgery than those with timing no more than 30 min. The blue color of methylene blue-stained SLNs sustained both in vivo and ex vivo, compared with the gradually faded blue color of patent blue that detected in 3 of 4 cases unilaterally. In the total of 112 dissected sides, the most common location of SLNs was the obturator basin (65.2%, 73/112), followed by external iliac area (30.4%, 34/112) and internal iliac area (26.8%, 30/112). Three patients who gave false negative results all had enlarged nodes.

Methylene blue is an effective tracer to detect SLNs in patients with early stage cervical cancer. The ideal dose and timing of methylene blue application are 4 ml and 60-90 min prior surgery, respectively.