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Encyclopedia of cancer (2015)
Metastatic pancreatic cancer; Metastatic PDAC; Pancreatic cancer metastases; Pancreatic ductal adeno- carcinoma metastasis
Pancreatic cancer metastasis describes the process that leads to secondary malignant tumor cell growth at distant sites or organs from the parental cancer in the pancreas. Pancreatic cancer is often used as a synonym for pancreatic ductal adenocarcinoma (PDAC), which is the most frequent (>80 %) and most lethal histologic type of cancer arising in the pancreas. Other histologic types are neuroendocrine tumors of the pancreas, acinar cell carcinoma, or adenosquamous carcinoma, which are not referred to in this entry.
Pancreatic cancer is the fourth leading cause of cancer-related death in the Western world, and one main reason for the dismal prognosis is early metastasis to regional lymph nodes and distant organ sites (most frequently to the liver, peritoneum, and lung) (Iacobuzio-Donahue et al. 2009) (Fig. 1). Macroscopically, distant PDAC metastases appear as whitish, hard nodules in the surrounding tissue. At diagnosis, pancreatic cancer is already metastasized in over 80 %, and only 1–2 % of patients with distant metastases survive longer than 5 years (Siegel et al. 2013). Autopsy studies revealed that the vast majority of patients die from metastatic disease: 70 % when all tumor stages are considered (Iacobuzio-Donahue et al. 2009). Furthermore, 75 % of patients who had undergone curative resection of the primary tumor developed distant metastasis; others developed peritoneal carcinomatosis or local recurrence.
Accordingly, the presence of lymph node or distant metastases negatively affects patient survival after curative resection, and several studies have underlined the prognostic value of the lymph node ratio, which is calculated by the number of tumor-inﬁltrated lymph nodes divided by the total number of surgically resected lymph nodes (Hartwig et al. 2011).
Metastatic spread is the most critical determinant of resectability of pancreatic cancer. Cross-sectional imaging using contrast-enhanced computed tomography (CT) or magnetic resonance imaging (MRI) is the mainstay for diagnosis and treatment allocation of pancreatic cancer patients; it allows identiﬁcation of locally advanced tumor growth or distant metastasis (Fig. 2).
Fig. 1. Immunohistological image of metastatic pancreatic ductal adenocarcinoma to a regional lymph node; brownish adenocarcinoma cells on the left inﬁltrate the lymphatic tissue (right)