Positive lymphoscintigraphy (ILS) and negative computed tomography for metastatic penile cancer

Penile carcinoma usually occurs in older than 40 years men with an incidence in western communities of 0.5 to 1.6 per 100,000 men per year while in developing countries the rate is much higher in men. Extensive lymph node dissection of lymphatic inguinal metastases evident by inguinal lymphoscintigraphy (ILS) induces improved overall survival. A 75 years old male with penile squamous cell carcinoma stage pT2N0M0 of less than 2cm diameter, with tumor invasion of the penis corpora underwent partial penectomy with a 2-cm disease-free margin. Three months postoperation, computed tomography (CT) was negative for local recurrence or distant metastases. A dynamic ILS was performed after local anaesthesia and intradermal injection of 80MBq of (99m)Tc-nanocolloid at the lower edge of the left and right inguinal ducts. The lymphatic chain and a hot spot suggestive of a first draining lymph node appeared after 15min on the right inguinal region in the second zone according to Daseler mapping. The left inguinal area was negative for sentinel node (SN). In view of this finding an exploratory laparotomy was performed and pathology showed that this lymph node that was probably a SN was infiltrated by the squamous cell carcinoma. The patient was upstaged to T2N1M0 and scheduled to receive adjuvant chemotherapy with two courses of cisplatin and 5-fluorouracil. While T1 and T2 tumours of diameters <2cm are best treated with penile-preserving methods such as circumciand/or local excision. Tumours of T2 >2cm, T3 tumours, and T4 tumours are treated with glans amputation and/or partial or total penile amputation. Imaging with magnetic resonance imaging (MRI) or computed tomography (CT) scan do not always give accurate staging information, because positive findings are usually found only in patients with clinically palpable, enlarged inguinal lymph nodes. Computed tomography and MRI have low sensitivity to identify occult metastases, because they present criteria for malignant involvement mainly based on the size of the lesions. The main pitfall of these diagnostic modalities is due to occult metastatic disease occurring within normal sized nodes. Approximatively 20% of the patients with non palpable lymph nodes harbour occult inguinal metastases, and there is evidence that this group of patients may benefit from early surgical dissection of the inguinal nodes, compared to a wait-and-see policy. It is understood that current imaging techniques cannot accurately detect occult metastases, while ILS is more reliable. In 80% of patients with penile cancer, after ILS, drainage to both groins is observed. Bilateral nodes are often visualized early, sometimes asynchronously with one of the lymph nodes filling late. This is why delayed images are recommended. Pitfalls of ILS are: a) Contamination of the skin with the tracer and b) radiopharmaceutical entering the blood. There are also several reasons that may account for absent or faint SN uptake: low dose of the tracer or low tracer quality, patient's age (better in young patients), tumor involvement of the sentinel node, and finally too short or too long interval between tracer injection and ILS. The ILS can be mapped according to Daseler's inguinal zones. Penile cancer drains directly to the nodes in the superior and central Daseler zones. According to others, the majority (73%) of SN was located in the medial superior, 8.7% in the lateral superior, and 18.3% in the central zone. No drainage was seen on the two inferior quadrants. The majority (62.1%) of higher-tier nodes was found in the external iliac zone. Inguinal LS can save us from watchful waiting in cases of otherwise occult metastases. In conclusion, ILS has shown lymph node metastases while clinical and CT examinations were negative. The false positive and false negative results of ILS are mentioned.