Patient and tumor characteristics
The clinicopathologic data of the evaluated cases are summarized in Table 1. Mean age of the patients was 63 years (ranging from 36 to 82). There were 76 male patient cases and 50 female patient cases (M:F=1.52:1). Originally, the epicenter of the tumor was diagnosed as periampullary duodenum in 3 cases, AOV in 37 cases, pancreatic head in 37 cases, distal CBD in 47 cases, and proximal CBD in 2 cases. After pathological revision, the epicenter of the tumor was AOV in 34 cases, pancreatic head in 44 cases, and distal CBD in 48 cases (Table 1). Changes in the original and revised diagnoses have been described in the following section and summarized in Table 2.
Grossly, 20 cases (15.9%) were categorized as fungating type, 93 (73.8%) as infiltrative, 3 (2.4%) as ulcerofungating, 5 (4.0%) as sessile, and 2 (1.6%) as solid type. The mean tumor size was 3.2 cm (ranging from 0.6 to 8.0 cm). Since tumor size (> 4.5 cm) is one of the important prognostic markers for pancreatic cancer, the cases were divided into two groups based on tumor size (< or > than 4.5cm) and compared. There were 96 cases with smaller tumor size (76.2%) and 30 cases with larger tumor size (23.8%). Tumor classification based on N stage according to the AJCC staging system, showed that 73 cases (57.9%) were N0, 53 were N1 (42.1%), and there were no N2 cases. M stage classification indicated that 8 cases (6.3%) were M1, while the rest was M0 (117 cases, 93.7%). Lymphatic invasion was found in 56 cases (44.4%), vascular invasion in 16 (12.7%), and perineural invasion in 72 cases (57.1%). Positive radial resection margin was found in 8 cases (6.3%). Tumor ulcer was found in 10 cases (7.9%).
Classification according to histologic grade showed that originally, 37 cases (29.4%) were diagnosed as well-differentiated tumors, 79 (62.7%) as moderately differentiated, and 10 as (7.9%) poorly differentiated. After review, 32 (25.4%) were well-differentiated, 90 (71.4%) were moderately differentiated, and 4 (3.2%) were poorly differentiated. In histologic subtypes, 34 cases (27.2%) were pancreaticobiliary subtype, 58 (46.4%) were more likely to be pancreaticobiliary subtype, 19 cases (15.2%) were more likely to be intestinal subtype, and 14 cases (11.1%) were of the intestinal subtype. Degree of accompanying fibrosis, known as desmoplastic reaction, was absent in 4 cases (3.2%) in the original pathologic reports, mild in 20 cases (15.9%), moderate in 72 cases (57.1%), and severe in 30 cases (23.8%). After revision, it was absent in 1 case (0.8%), mild in 35 cases (27.8%), moderate in 57 cases (45.2%), and severe in 33 cases (26.2%). Degree of peritumoral inflammation was mild in 53 cases (42.1%) in the original pathologic reports, moderate in 62 cases (49.2%) and severe in 11 cases (8.7%). After revision, it was mild in 42 cases (33.3%), moderate in 70 cases (55.6%), and severe in 14 cases (11.1%). Tumor recurrence was observed in 61 cases (48.8%) during an average follow-up of 969.7 days (ranged 3 to 5234 days). Disease-free survival duration was an average of 731.2 days (ranging from 3 to 4173 days). Eighty-seven out of 126 patients (69.0%) were dead during the follow-up.
Comparison of tumor epicenter and T stages between original and revised diagnoses
Comparison of original and revised diagnoses showed that the epicenter of the tumor was altered in 22 out of 126 cases (17.4%) (Table 2). Among the 22 cases, 10 cases showed a discrepancy between distal CBD and pancreatic head cancers, 6 cases showed a discrepancy between distal CBD and AOV cancers, 5 cases showed a discrepancy between pancreatic head and AOV cancers, 2 cases showed a discrepancy between periampullary duodenum and AOV, 2 cases showed a discrepancy between proximal and distal CBD, and 1 case showed a discrepancy between periampullary duodenum and distal CBD. As the tumor locations have been changed after the review, the T stages were also altered (Table 2). As a result, 6 cases showed different T stage between the original and revised diagnoses with 3 overstaged and 3 understaged cases, respectively (6 out of 126 cases, 4.8%).
Immunohistochemical staining and immunoreactivity results
The immunohistochemical staining conditions are summarized in Table 3 and the representative images of the immunohistochemical stainings are shown in Supplementary Figure 1. The immunoreactivity of SOX2 in the nucleus was negative in 13 cases (10.3%), 1+ in 66 cases (52.4%), 2+ in 45 cases (35.7%) and 3+ in 2 cases (1.6%). The SOX2 immunoreactivity in the cytoplasm was negative in 66 cases (52.4%), 1+ in 56 cases (44.4%), 2+ in 4 cases (3.2%), and no cases showed 3+. CD24 staining was negative in 6 cases (4.8%), 1+ in 79 cases (62.7%), 2+ in 37 cases (29.4%), and 3+ in 4 cases (3.2%). Oct4 immunoreactivity was 1+ in 26 cases (20.6%), 2+ in 73 cases (57.9%), and 3+ in 27 cases (21.4%). IGF-1 staining was negative in 13 cases (10.3%), 1+ in 74 cases (58.7%), 2+ in 33 cases (26.2%), and 3+ in 6 cases (4.8%). The FGFR1 immunoreactivity was 1+ in 7 cases (5.6%), 2+ in 52 cases (41.3%), and 3+ in 67 cases (53.2%). The VEGF immunoreactivity was 1+ in 18 cases (14.6%), 2+ in 78 cases (63.4%), and 3+ in 27 cases (22.0%). CD44v6 staining was negative in 14 cases (11.1%), 1+ in 41 cases (32.5%), 2+ in 43 cases (34.1%), and 3+ in 28 cases (22.2%).
Clinicopathological parameters related to tumor recurrence
There was no significant difference between the recurrence and non-recurrence groups based on age, gender, original, revised and combined locations, gross type, ulcer, tumor size, presence or absence of radial resection margin, N stage, and M stage. Although there were no statistically significant relationships between T stage and recurrence, there was a tendency that the recurrence group had a higher T stage than the non-recurrence group. Moreover, there was no statistically significant difference observed between the pathological parameters such as lymphatic invasion, vascular invasion, perineural invasion, histological deferentiation, degree of fibrosis, degree of inflammation, histological subtype and the markers detected by IHC (CK7, CK20, CDX-2, MUC-2, SOX2 (nuclear), SOX2 (cytoplasmic), CD24, Oct4, IGF-1, FGFR1, VEGF, and CD44v6). However, the only significant difference was observed in the original degree of fibrosis (p=0.020) as indicated in Table 4. However, the multivariable regression analysis showed no statistical differences among all clinicopathological parameters according to tumor recurrence (data not shown).
Disease-free survival analysis in recurrence patient
The clinical parameters such as age <74 (p=0.0221), location of AOV (p=0.014), lower T stage (p=0.02), size less than 1.5 cm (p=0.0426), lower N stage (N0) (p=0.000391) were significantly associated with better disease-free survival (DFS) in recurrent patients, whereas, no significant correlation was observed in other parameters (Supplementary Figure 2).
In addition, other pathological parameters including no lymphatic invasion (p<0.0001), histological well differentiation (p=0.00121), intestinal subtype (p=0.0417), and mild fibrosis (p=0.0259) showed a significant association with better DFS (Supplementary Figure 3). In addition, IHC markers such as CDX-2 (p=0.0245) and FGFR1 (p=0.0181) were also significantly correlated with better DFS (Supplementary Figure 4). Cox regression analysis showed no significant relation of any clinicopathologic parameters to DFS (data not shown).
Clinicopathological parameters related to overall survival
Among clinical parameters, age (p=0.0527) and gender (p=0.908) were not associated with overall survival. On the other hand, location of AOV (p<0.0001), lower T stage (p=0.000228), sessile and solid gross type (p=0.00278), size less than 1.5 cm (p=0.00727), lower N stage (N0) (p<0.0001), and lower M stage (M0) (p=0.000139) were significantly related to better overall survival (Figure 1). Among pathological parameters, better overall survival was related to no lymphatic invasion (P<0.0001), no vascular invasion (p=0.000325), no perineural invasion (p=0.00145), histological well differentiation (p=0.000793), intestinal subtype (p=0.000483), no fibrosis (p=0.00497), and severe inflammation (p=0.036) (figure 2). In addition, expression of four IHC markers, higher expression of intestinal-type markers, CK20 (p=0.0135) and CDX2 (p=0.000135), and higher expression of EMT markers, FGFR1 (p=0.0014) and VEGF (p=0.0333) were significantly related to better overall survival (Figure 3). The combined panel expression score more than 8 of CK20, CDX2, FGFR1, VEGF, and IGF-1 was significantly related to better overall survival (p=0.000445) as well as the combined panel expression score more than 6 of CK20, CDX2, FGFR1, and VEGF (p<0.0001) (Figure 3). Cox regression analysis also showed a significant relationship of N stage, lymphatic invasion, degree of inflammation, pancreaticobiliary/intestinal subtypes, expression of intestinal markers, CK20 and CDX2, and EMT markers, FGFR1 and VEGF (Supplementary Table 2, Supplementary Figure 5).