Which of the following is dynamic sentinel lymph node biopsy (DSLNB) for staging in patients with proven SCC of the penis indicated for?
A. Clinically palpable inguinal lymph nodesAnswer C
In patients with clinically impalpable inguinal nodes at presentation, around 20% will harbour occult lymph node metastases. If all patients went onto have inguinal lymph node dissections 80% would be over treated and exposed to the morbidity of surgery. In an attempt to identify the 20% of patients with metastatic disease and avoid the unnecessary morbidity in the other 80% the technique of DSLNB was developed.
It is well accepted that penile cancers spread by embolisation via the lymphatics in a predictable stepwise fashion to the inguinal and then to the iliac nodes. The concept of sentinel lymph node biopsy was first described in men with penile cancer in 1977 by Cabanas. Unfortunately, due to a high false negative rate (FNR) and lack of reproducibility the technique fell out of favour until several modifications were made in the mid 1990s. The FNR of the DSLNB technique in penile cancer patients has been reduced to around 5%. The technique has been shown to be reproducible and has a short learning curve in the hands of penile cancer centres.
To identify the SLN pre operative mapping with Technetium 99m (Tc99m) labelled nanocolloid is essential. Intra operatively a handheld gamma probe is used to detect the ‘hot’ nodes and injected patent blue dye helps visualise the SLNs. The addition of preoperative ultrasound and fine needle aspiration cytology, intraoperative palpation and immunohistochemical stains have also helped to reduce the FNR.