Objective: To evaluate dynamic sentinel lymph node biopsy (DSLNB) in patients with squamous cell carcinoma (SCC) of the penis and palpable inguinal lymph nodes, using inguinal lymph node dissection (ILND) as the reference standard to assess the reliability of DSLNB, as using radioscintigraphy and colloidal blue-dye injection to locate the SLN was reported to be a useful technique to avoid ILND in men with SCC of the penis and clinically impalpable nodes.
Patients and methods: The study included 23 consecutive men with SCC of the penis and clinically palpable inguinal nodes treated between August 1999 and July 2006. On the day before surgery the patient had the SLN located by subcutaneous injection of 60 MBq (99m)Tc-nanocolloid 2 cm proximal to the penile tumour. The following day the patient was taken to the operating room for DSLNB, resection of the penile tumour and simultaneous ILND, if considered indicated (G2-3 and/or T3-4 primary tumour). During surgery 2 mL of colloidal blue dye was injected in the same area as the previous (99m)Tc-nanocolloid injection. The SLNs were located during surgery using a gamma-probe and visualization of blue dye in the node(s), which were then surgically removed. After partial or total penectomy, selected patients had ILND through a 10-cm subinguinal incision. The primary tumour, SLNs and ILND specimens were assessed histopathologically, using haematoxylin and eosin staining only.
Results: Biopsy of the primary tumour showed SCC grade 1 in six, grade 2 in 13 and grade 3 in two patients. The clinical T stage was T1 in two, T2 in seven, T3 in 13 and T4 in one. There were clinically palpable inguinal lymph nodes bilaterally in 19 and unilaterally in four men. Scintigraphy before surgery showed inguinal nodes bilaterally in 12 and unilaterally in eight patients, while there were no nodes in three. Surgery comprised partial penectomy in 14, radical penectomy in eight and circumcision alone in one patient. Simultaneous bilateral ILND was done in 15 patients. Inguinal node metastases were present in four of the 23 (17%) patients; the SLN was falsely negative in three (13%), one of whom had a small focus of cancer in the SLN that was missed on initial histopathological examination, and in two the dynamically located SLN contained no cancer, but node metastases were found in the ILND specimen.
Conclusion: The relatively high false-negative rate of DSLNB indicates that it is not sufficiently reliable to replace complete ILND in men with a high suspicion of nodal metastases, i.e. a high-grade or high-stage primary lesion with clinically palpable inguinal nodes.