Discussion
Breast cancer is the cancer with the highest incident rate in women according to the Global Cancer Statistics in 20201. Breast cancer often metastasizes to other organs, particularly the lungs, bones, liver, and brain, and, very rarely, the bile duct. Thus far, 16 cases of bile duct metastasis of breast cancer have been reported in detail. These case reports were obtained through a search of PubMed for articles published from 1946 to 2021, using the search terms “breast cancer” and “biliary metastasis”. In addition to these, Japanese case reports were obtained through a search of the Japana Centra Revuo Medicina Web for articles published from 1977 to 2021, using the Japanese equivalents of the search terms mentioned above2-13. The details of these case reports are presented in Table 1. The average age of the patients was 56 years (42–70 years). Most cases were examined for subjective symptoms, such as jaundice (11/16), abdominal pain (3/16), and pruritus (3/16), and only one case was asymptomatic. The mean time to metastasis to the bile duct was 7.4 years (2–21 years), and most of the cases further showed metastasis to other organs such as the gallbladder, liver, and bones. Many of the reported cases required multiple examinations for diagnosis. In reports before the 1990s, most cases were diagnosed by histology of resected specimens after surgery; however, recently, some cases were diagnosed by ERCP.
Regarding treatment for objective jaundice by bile duct stenosis, only five cases were treated by endoscopic drainage (Table 2)2,3,5,6. On cholangiography, all the reported cases with available images showed severe diffuse stenosis confined to a relatively long segment of the bile duct. In four of these cases, tissue biopsy or brushing cytology at the stenotic area was performed, all of which led to a definitive diagnosis. Conversely, Coletta et al., reported a case of bile duct metastasis of breast cancer, in which endoscopic cytological examination of the stenotic area was negative; histologic examination of the resected specimen after surgery revealed tumor cells on the outer side of the bile duct, but not on the bile duct endothelium7. In such cases, it is difficult to make a definitive diagnosis based on endoscopic bile duct biopsy or brushing cytology alone; therefore, a comprehensive approach based on clinical history and findings on other imaging modalities are required. Our case is the first to describe the duration of stent patency, and in which stent stenosis due to tumor invasion was observed repeatedly within a short period. There was a previous case report of gastric metastasis of breast cancer, in which an SEMS was placed for pyloric stenosis, and obstruction due to tumor invasion was observed barely 3 months later14. This indicates that in the case of breast cancer metastasis, in-stent invasion may occur earlier. Furthermore it may be useful to place SEMS in the early stages after diagnosing biliary metastasis, as it is superior to plastic stent from the viewpoint of stent patency. Regarding complications, cholecystitis occurred in two of reported cases after endoscopic stenting; however, other serious adverse complications were not reported. Prognosis varied from case to case, depending on the degree of progress of breast cancer and metastases.
In summary, we encountered a rare case of bile duct breast cancer metastasis, in which obstructive jaundice was effectively managed by endoscopic drainage. Endoscopic bile duct stenting is less invasive than surgical operation, making it an effective treatment option.