Lymphatic drainage from renal cell carcinoma along the thoracic duct visualized with SPECT/CT

Lymphatic drainage of renal cell carcinoma is unpredictable. Renal lymphatics directly joining the thoracic duct without traversing any lymph nodes have been described in cadaver studies, yet to date, this has never been visualized using functional imaging in vivo.

Patients with renal tumors <10 cm (cT1-cT2) and clinical absence of metastases (cN0, cM0) took part in a prospective institutional review board approved study investigating sentinel node mapping. After ultrasound-guided percutaneaus intratumoral injection of (99m)Tc-nanocolloid (0.4 mL, 200 MBq) the day before surgery, planar sequential lymphoscintigraphy was obtained after 20 min and 2-4 h. Subsequently, SPECT/CT imaging was performed. Of 42 patients, 4 showed early lymphatic drainage following the course of the thoracic duct on lymphoscintigraphy and SPECT/CT images. In one patient, this was observed without any retroperitoneal lymph node interposition. In relation to patients with sentinel nodes on SPECT imaging the frequency of this drainage pattern was (4/22) 18.2%.

SN mapping of renal tumors using functional imaging modalities such as lymphoscintigraphy and SPECT/CT enables identification and sampling of sentinel nodes outside the area of routine dissection. Direct aberrant drainage through the thoracic duct can be observed in vivo as demonstrated in this study. This may support a hypothesis for certain anatomical metastatic sites and the failure to demonstrate a survival benefit of retroperitoneal lymph node dissections in renal cell carcinoma.