Molecular, morphological and survival analysis of 177 resected pancreatic ductal adenocarcinomas (PDACs): Identification of prognostic subtypes

Abstract

Pancreatic ductal adenocarcinoma (PDAC) has generally a poor prognosis, but recent data suggest that there are molecular subtypes differing in clinical outcome. This study examines the association between histopathologic heterogeneity, genetic profile, and survival. Tumor histology from 177 resected PDAC patients with follow-up data was subclassified according to predominant growth pattern, and four key genes were analyzed. PDACs were classified as conventional (51%), combined with a predominant component (41%), variants and special carcinomas (8%). Patients with combined PDACs and a dominant cribriform component survived longer than patients with conventional or other combined PDACs. Genetic alterations in at least two out of four genes were found in 95% of the patients (KRAS 93%, TP53 79%, CDKN2A/p16 75%, SMAD4 37%). Patients with less than four mutations survived significantly longer (p = 0.04) than those with alterations in all four genes. Patients with either wildtype KRAS or CDKN2A/p16 lived significantly longer than those with alterations in these genes (p = 0.018 and p = 0.006, respectively). Our data suggest that the number of altered genes, the mutational status of KRAS and certain morphological subtypes correlate with the outcome of patients with PDAC. Future pathology reporting of PDAC should therefore include the KRAS status and a detailed morphological description.

Figure 1. Spectrum of histologic patterns in pancreatic ductal adenocarcinomas (PDACs).

(A) Conventional PDAC. (B–F) Combined PDACs with a dominant histological component: (B) Clear-cell component. (C) Cribriform component. (D) Gyriform component. (E) Micropapillary component. (F) Complex component. (G) Adenosquamous carcinoma. (H) Colloid carcinoma. (I) Papillary carcinoma.

Figure 2. Tubular adenocarcinoma of the pancreas.

(A) Low power view showing groups of well-differentiated infiltrating tubules surrounded by small cuffs of desmoplastic stroma. (B) Infiltrating well differentiated neoplastic glands closely imitating normal ducts.

Figure 3. KRAS mutation analysis (direct sequencing) of codon 12 of exon 2.

(A) Hotspot of exon 2 shows KRAS wildtype, (B) KRAS mutation (p.G12D, arrow), or (C) low-level mutation (p.G12C, arrow, faint red signal), as confirmed by next generation sequencing (NGS) (case #190).

Figure 4. TP53 analyses.

(A,B) TP53 wildtype is associated with nuclear TP53 expression in up to 24% of neoplastic cells. (C,D) TP53 missense mutation (p.Y205C; exon 6) is associated with nuclear TP53 overexpression in ≥25% of neoplastic cells (mutation type 1). (E,F) TP53 intragenic deletion or nonsense, frameshift or splicesite mutations (mutation type 2; here represented by an insertion-frameshift mutation p.P153*fs28; exon 5) is associated with loss of nuclear TP53 expression in neoplastic cells.

Figure 5. Immunohistochemical analysis of CDKN2A/p16 and SMAD4.

(A) Strong nuclear and cytoplasmatic staining of CDKN2A/p16 in neoplastic cells indicating the presence of an intact gene. (B) No labeling of CDKN2A/p16 in neoplastic cells indicating either a deletion, inactivating mutation, or promoter hypermethylation. (C) Nuclear SMAD4 immunolabeling of neoplastic cells indicating the presence of an intact protein. (D) Loss of SMAD4 expression in >90% of neoplastic cells indicating a deletion or inactivating mutation of the gene.

Figure 6. Kaplan-Meier survival curves in pancreatic adenocarcinomas correlated with molecular status.

(A) Significant correlation of median patient survival with number of mutations. (B) Patients with KRAS wildtype have a significantly better overall survival than patients with mutated KRAS. (C) Patients with intact CDKNA2/p16 have a significantly better overall survival than patients with altered CDKNA2/p16.

Figure 7. Risk stratification after surgical resection of PDAC.

Proposed scheme to identify PDACs with low/intermediate and high biological aggressiveness based on morphological classification and molecular testing of key genes.