SRCC is composed almost exclusively of poorly cohesive neoplastic epithelial cells containing intracytoplasmic mucin that displaces the nuclei towards the periphery. SRCC of the pancreas is extremely rare and has a very poor prognosis . According to the study using the Surveillance, Epidemiology, and End Results database from 2000 to 2014, the incidence of pancreatic SRCC is 0.4–0.5% among all cases of pancreatic carcinoma . Among the eight cases reported thus far (Table 1) [4–11], surgical treatment with radical resection, pancreatoduodenectomy, and/or total pancreatomy could be performed in four cases, and there was only one case of borderline-resectable tumor treated with neoadjuvant chemotherapy with gemcitabine.
Two studies have reported on the prognosis of patients with pancreatic SRCC. In the first, where the prognosis was investigated according to the tumor location (esophagus, stomach, small intestine, appendix, colon, and rectum), the group with pancreatic SRCC had the worst median overall survival (3.4 months) . The second study evaluated the predictive effects of epidemiological factors and treatment interventions on the overall survival. The 1-, 2-, and 5-year overall survival rates were 17%, 9%, and 4%, respectively, and surgical interventions (pancreatectomy and pancreatomy with radiation therapy, no case with adjuvant therapy) were associated with improved overall survival .
To the best of our knowledge, the present is the first report of adjuvant chemotherapy and long-term postoperative survival in pancreatic SRCC. We performed adjuvant chemotherapy with S-1, which is an oral fluoropyrimidine that contains tegafur, a prodrug of 5-fluorouracil, gimeracil, and oteracil potassium. The efficacy of S-1 for improving the postoperative survival has been reported in gastric cancer , which has the highest incidence of SRCC among gastroenterological tumors , and pancreatic cancer . According to the Japanese guidelines, adjuvant chemotherapy with S-1 is recommended for gastric and pancreatic cancer [14–15]. The difference in the therapeutic regimens for the two types of cancer is the length of drug administration; 1 year for gastric and 6 months for pancreatic cancer. However, SRCC of the pancreas has a higher risk of recurrence and poorer survival rates than those of typical ductal adenocarcinoma ; therefore, we scheduled and performed 1-year adjuvant therapy.
In summary, we report a rare case of pancreatic SRCC with long-term survival. This case indicates that radical resection and adjuvant chemotherapy with S-1 may be an important treatment strategy for resectable pancreatic SRCC.