Intraductal tubulopapillary neoplasm accompanied by invasive carcinoma of the pancreas: A case report and review of the literature.

Intraductal tubulopapillary neoplasms (ITPNs) are rare pancreatic neoplasms accounting for ~0.4% of pancreatic tumors. However, their clinicopathological characteristics have not been clearly determined and the number of available clinical studies on this type of tumor is limited at present. Due to the rare incidence of ITPN, diagnosis is often delayed. We herein present a unique case of a 38-year-old man who was diagnosed with ITPN accompanied with invasive carcinoma of the pancreas and underwent total pancreatectomy. The morphological characteristics of ITPN include closely packed tubular glands, without mucin secretion, accompanied with invasion of the loose connective tissue. The immunohistochemical staining suggested that the tumors did not originate from the gastrointestinal tract but rather from the bile duct. In addition, the Ki-67 positive staining rate of tumor cells was <20%. The microsatellite instability analysis demonstrated microsatellite stability, without detected gene mutations of epidermal growth factor receptor, Kirsten rat sarcoma viral oncogene homolog, neuroblastoma RAS viral oncogene homolog or B-Raf proto-oncogene. However, a mutation was identified in exon 9 of the P53 gene, the most frequently mutated gene in human cancer, which suggested the underlying mechanism of ITPN. On the basis of this case, the aim of this study was to summarize and review the relevant reports of ITPNs in recent years, in order to investigate the clinicopathological characteristics and differential diagnosis of ITPN.