Pancreatic malignant fibrous histiocytoma, inflammatory myofibroblastic tumor, and inflammatory pseudotumor related to autoimmune pancreatitis: characterization and differential diagnosis

Abstract

Malignant fibrous histiocytoma (MFH) and inflammatory myofibroblastic tumor (IMT) are uncommon primary non-epithelial cell tumors of the pancreas. In addition, there are inflammatory pseudotumors (IPT) that may arise in the course of autoimmune pancreatitis (AIP). In the English language literature, only 24 cases of IMT and nine cases of MFH in the pancreas have been reported to date. We investigated three individual spindle cell tumors of the pancreas that were identified as MFH, IMT, and IPT, respectively, using immunohistochemical and molecular analysis. Both the MFH and the IMT, but not the IPT, showed nuclear p53 expression and mutations of the p53 gene. The MFH and the IMT also had higher mitotic and Ki-67 (MIB-1) indexes than the IPT. The IPT was found to be a tumor-like case of AIP. Many IgG4-positive plasma cells, which are considered to be a feature of AIP, were found in all three tumors. It is concluded that in this series of spindle cell tumors of the pancreas, apart from immunohistochemical features, the demonstration of p53 mutations may be helpful in distinguishing true neoplastic tumors from pseudotumors such as IPTs arising in the context of AIP.

Chronic pancreatitis, pseudotumors and other tumor-like lesions

“…[103][104][105] Judging from the descriptions and illustrations of these cases, these changes appear to be compatible with those seen in autoimmune pancreatitis. 99 As the clinical features of the reported inflammatory pseudotumors of the pancreas are also very similar, it is likely that these lesions may represent an advanced stage of autoimmune pancreatitis in which the fibrotic changes predominate and the disease focuses on a certain area. 11 The fact that inflammatory pseudotumors showing sclerosing cholangitis have been observed in the liver hilus 106 suggests that there is possibly an idiopathic pancreatobiliary inflammatory disease complex whose facets include autoimmune pancreatitis, extrahepatic sclerosing cholangitis and inflammatory pseudotumor of the pancreas and/or the common bile duct.…”

“…99 These tumors have to be distinguished from malignant fibrous histiocytoma and true inflammatory myofibroblastic tumor. Inflammatory pseudotumors may occasionally be seen in paraduodenal pancreatitis and other rare inflammations such as mycobacterial infection.…”

“…If the fibrotic changes occupy large areas that show myofibroblasts in a storiform arrangement, they may mimic the features of an inflammatory pseudotumor. 98,99 In addition to the duct changes and the sclerotic process, there are vascular changes. Most frequent is vasculitis affecting the small veins ( Figure 18).…”

Spontaneous Development of a Pancreatic Exocrine Disease in CD28-Deficient NOD Mice

“…3 is a distinct form of chronic pancreatitis that, until recently, had been described heterogeneously as non-alcoholic duct-destructive chronic pancreatitis, sclerosing pancreatitis, lymphoplasmacytic sclerosing pancreatitis, pancreatic inflammatory pseudotumor, or other morphological descriptions (1)(2)(3)(4)(5)(6)(7). The notion that this syndrome has an autoimmune etiology stems from early studies where AIP develops in association with several autoimmune diseases, including hypergammaglobulinemia, Sjögren's syndrome, rheumatoid arthritis, inflammatory bowel disease, diabetes, and sclerosing cholangitis, among others (7)(8)(9)(10)(11)(12)(13)(14).…”

Primary Pancreas Sarcoma, Optimal Treatment and Prognostic Factors

“…Three patients had leiomyosarcoma and one case had inflammatory myofibroblastic tumor. All had undergone complete tumor removal and none received adjuvant treatment (4)(5)(6).…”