Previous studies have noted that the predominant sites of metastasis for PDAC are the lymph node, liver, lung, and peritoneum [4, 5]. We described a rare case of metachronous gastric and gallbladder metastases from pancreatic body cancer. Gastric metastasis of PDAC is rare. To our knowledge, only three cases have been reported in the English literature [6,7,8]. Oda et al. performed autopsies on 209 patients with PDAC and reported that gastric metastasis was found in only two cases [9].
Generally speaking, there are five metastatic pathways to the stomach: (1) direct invasion, (2) intraoperative seeding, (3) hematogenous metastasis, (4) lymphatic metastasis, and (5) intraluminal or intramural dissemination [10]. In our case, the primary pancreatic tumor was not anatomically near the stomach, and resection with tumor-free margins was performed. In addition, the two metastatic lesions in the subserosa and muscularis propria of the stomach did not expose to the mucosa or serosa. Considering these facts, we thought that gastric metastasis occurred through the hematogenous pathway.
Gallbladder metastasis of PDAC is also rare. This appears to be the first report of resected gallbladder metastasis from PDAC in the English literature. An autopsy study by Kishi et al. demonstrated a 7.4% incidence of gallbladder metastasis among patients with PDAC [11]. Yoon et al. surveyed 417 patients with pathologically confirmed gallbladder malignancies; 20 (4.8%) were metastatic (stomach, n = 8; colorectum, n = 3; liver, kidney, and skin, n = 2 each; and others, n = 3) [12]. In our case, as the tumor was subserosal and did not expose to the mucosa, hematogeneous metastasis was most likely, as with the gastric metastases. Although Yoon et al. also reported that the prognosis of metastatic gallbladder carcinoma was poor, with 8.7 months of median overall survival [12], our case resulted in long-term survival after surgical resection.
There was a possibility that cancer cell seeding by FNA was the cause of gastric metastases. However, we think it unlikely because one of the metastases was located in the antrum, far from the aspiration site, and we also found a gallbladder metastasis which could not have been related to FNA.
Surgical resection for disease relapse of PDAC remains debatable due to lack of evidence of survival benefit. Recently, several studies showed survival benefit of surgical resection for PDAC recurrence. Miyazaki et al. showed a prolonged survival by repeat pancreatomy for isolated local recurrence [13]. Thomas et al. highlighted a single tumor as a key factor benefiting most from re-resection for lung metastasis from PDAC [14].
In the case presented here, we first diagnosed solitary lymph node recurrence of PDAC after pancreatectomy by CT imaging and performed surgical resection after chemotherapy. Unintentionally, two gastric metastases and one gallbladder metastasis were resected with tumor-free margins. This patient’s survival of more than 3 years suggests the benefit of surgical intervention in combination with systemic chemotherapy. However, specific selection criteria for resection for multiple metastases remain unclear.
