Clinicopathological study of surgery for pulmonary metastases of hepatoblastoma with indocyanine green fluorescent imaging

Background: The prognosis of metastatic hepatoblastoma remains poor; to improve it, pulmonary metastasis must be controlled. Indocyanine green (ICG) fluorescent imaging has been used recently for lung metastasectomy. The objective of our study was to clarify the usefulness of ICG imaging for lung metastasectomy of hepatoblastoma using detailed clinicopathological analysis. Procedure: Patients with hepatoblastoma who underwent resection of pulmonary metastases with ICG fluorescent imaging were studied using retrospective analysis of clinical information, a review of their surgical records, and a histological analysis of their metastatic nodules. Results: Sixteen patients were enrolled. In total, 61 ICG-imaging-guided pulmonary metastasectomies were performed, and 350 ICG-positive and 23 ICG-negative specimens were identified. Tumors were confirmed in 250 of the ICG-positive specimens, including eight nonpalpable nodules, on microscopic examination. One hundred ICG-positive specimens and histologically tumor-negative specimens showed histological changes suggesting the regression of a tumor or bloodstream disturbance. The palpable ICG-negative tumors showed more-severe atypia than the ICG-positive tumors. Conclusions: This study demonstrates the high sensitivity of ICG imaging in detecting metastatic lesions of hepatoblastoma. Histological examinations suggested that ICG imaging detects not only tumor cells, but also nontumorous pulmonary tissues affected by bloodstream disturbance. Because a number of false-positive specimens were detected, further optimization of the dose of ICG and the timing of its administration may be required for thorough metastasectomy. Several false-negative specimens were also detected, suggesting the presence of ICG-negative metastatic tumors. Palpation during operation and imaging studies remain essential for detecting metastatic lesions, even in the era of ICG imaging.