Penile lymphoscintigraphy for sentinel node identification

Lymphoscintigraphy for sentinel node (SN) identification has been extensively validated in breast cancer and melanoma. The aim of this study was to evaluate the findings of lymphoscintigraphy for SN identification in carcinoma of the penis. Lymphoscintigraphy was performed in 74 consecutive patients (mean age 62.2 years, range 28-87 years) with clinically lymph node-negative squamous cell carcinoma of the penis (stage T2 or greater). Following local anaesthesia by xylocaine 10% spray, technetium-99m nanocolloid (mean dose 64.8 MBq, range 40-131 MBq) in a volume of 0.3-0.4 ml was injected intradermally around the tumour. Shortly after injection, a 20-min dynamic study was performed with a dual-head gamma camera; subsequently, static anterior and lateral images were obtained at 30 min and 2 h using simultaneous cobalt-57 flood source transmission scanning. 57Co-assisted skin marking defined SN location for gamma probe/blue dye-guided biopsy, which was performed the next day. The SN visualization rate was 97% (72/74). Lymphatic drainage was bilateral in 81% of the cases (58/72), exclusively to the left groin in 13% (9/72) and only to the right groin in 6%. Bilateral lymph node drainage was synchronous in 38% (22/58) and asynchronous in 62% (in 18 patients the initial route was the left groin, and in the other 18, the right groin). Visualization before 30 min occurred in 66 patients (93%), in 64 of them (88%) already during the dynamic study. A total of 173 SNs were visualized (85 in the right groin, 88 in the left groin). Pitfalls were caused by inguinal skin contamination during injection (four patients) and intracavernous administration (one patient). At surgery, a total of 161 SNs were identified and removed. Sixteen patients (22%) had a tumour-positive SN and underwent standard regional lymph node dissection subsequently. During follow-up (median 28 months, range 3-74 months), two patients with a negative SN developed lymph node metastases in the mapped basin. It is concluded that penile lymphoscintigraphy is a valid and well-tolerated method for lymphatic mapping and SN identification. Although bilateral early inguinal drainage is the most frequent pattern, late imaging is recommended principally in patients with initial unilateral drainage in order to exclude delayed lymph node filling in the contralateral groin. SN identification may lead to a more accurate staging and avoid extensive lymph node dissection in the majority of patients with penile carcinoma.