Indocyanine green to localize subpleural pulmonary relapse of hepatoblastoma during thoracoscopy

Relapsed hepatoblastoma continues to have a poor prognosis with early detection and complete surgical resection of any relapse essential.1 Pulmonary relapse is common yet often lesions are subpleural and difficult to identify with thoracoscopy. Indocyanine green (ICG) is a fluorescent anion, which is excitable at a light wavelength of 750–810 nm by the near infrared spectrum and hence fluoresces when infrared light is applied to it.2 ICG is taken up by normal hepatocytes but in hepatoblastoma cells, ICG excretion is abnormal, allowing detection and differentiation from adjacent tissues using modern near infrared detecting systems.3 The mechanism for this is the impaired ability of hepatoblastoma cells to excrete ICG into the biliary system when compared to normal surrounding liver tissue.4 This contrast is even more marked in the lung whose cells do not retain ICG, unlike the hepatocyte-derived neoplastic cells of hepatoblastoma where ICG is well absorbed. We utilized these properties of ICG to identify and resect a small subpleural pulmonary relapse of hepatoblastoma as an alternative to existing localization techniques. Written consent was obtained to publish clinical details and images of the following patient. A 1-year-old boy diagnosed with a PRETEXT III CPV localized hepatoblastoma with Alpha Feto Protein (AFP) of >300 000 at diagnosis had previously undertaken neoadjuvant therapy and orthotopic liver transplantation at another centre. Following a normalization of AFP post-transplant and adjuvant chemotherapy, a rising AFP was noted with CT scan demonstrating two coalesced small (5 mm) subpleural left upper lobe pulmonary nodules. Given the subpleural location, 24 h preoperatively, 0.5 mg/kg of ICG (Verdye, Diagnostic Green Ltd.) was administered intravenously. Four port thoracoscopy (3 × 5 mm, 1 × 12 mm) was performed under single lung ventilation using an infrared-detecting capable camera system (1688 AIM Platform, Stryker). On standard white light thoracoscopy the lesion was not visible (Fig. 1). However, upon activation of near infrared (NIR) mode, the lesion was clearly identifiable as a brilliant green fluorescent area (Fig. 2). A stapled wedge resection, utilizing an 8 mm stapler (Signia small-diameter reload, Medtronic), using the extent of fluorescence as a guide to obtaining a clear margin, was performed (Fig. 3). The specimen was retrieved via a catch bag and a chest tube placed. The patient was discharged on postoperative Day 3, histology demonstrated a 7 × 5 × 8 mm foci of hepatoblastoma with clear margins, and the patient continued adjuvant therapy with normalization of AFP. ICG is increasingly being used to localize a range of paediatric malignancies intraoperatively.3 It is of particular utility in both primary and metastatic liver tumours such as hepatoblastoma where uptake by tumour cells is especially avid. For suspected pulmonary relapse of hepatoblastoma, ICG can be delivered 24 h prior to the planned surgery and allowed localization of a lesion not visible on standard white light thoracoscopy. Due to the lack of tactile feedback during thoracoscopy, preoperative nodule localization is vital for lesions located below the pleural surface. This technique has benefits over existing methods of localization such as methylene blue (often spreads over a large pleural surface obscuring the field), metallic coil (difficult to identify intraoperatively), or hookwire (may move with transfer of patient or with single lung ventilation). It is however limited to lesions within 15 mm of the pleural surface of the lung due to the maximum penetration of infrared light through lung tissue.2 Fluorescence guidance using systemic ICG should therefore be considered in pulmonary metastectomy for small subpleural pulmonary metastases in hepatoblastoma. It allows excellent localization and facilitates complete surgical resection of these lesions during thoracoscopy and its use can be extended to other paediatric and adult malignancies where uptake of ICG occurs. I would like to thank the family who gave written consent for the clinical information and images to be published.