Benign Tumors and Tumorlike Lesions of the Pancreas
Section snippets
Overview: serous neoplasms
Serous neoplasms of the pancreas are rare benign tumors accounting for approximately 1% of all pancreatic lesions. These tumors reveal a unique cytomorphology characterized by distinctive cuboidal epithelial cells with uniform round nuclei, dense, homogeneous chromatin, and a prominent epithelium-associated microvascular meshwork.1, 2 They are generally regarded under the category of ductal-type tumors; however, they do not produce mucin despite their presumed ductal lineage, instead, they
Inflammatory myofibroblastic tumor
Inflammatory myofibroblastic tumor is a rare, especially in the pancreas, and distinctive entity.66, 67, 68, 69 The pancreatic head is affected most frequently by an ill-defined and firm mass causing obstructive jaundice. Therefore, patients are often suspected to suffer from pancreatic ductal adenocarcinoma.70, 71
At low-power magnification, inflammatory myofibroblastic tumor has a relatively pushing border (Fig. 7). Fibroblasts and myofibroblasts, usually arranged in a storiform pattern, with
Lymphoepithelial cyst
Lymphoepithelial cyst is usually asymptomatic, with the lesion found incidentally on imaging studies performed for unrelated reasons or at autopsy.77, 78 In contrast to its salivary gland analogues, no autoimmune disorder is identified and there is no syndrome association. Association with human immunodeficiency virus also appears to be coincidental and exceedingly uncommon.79
It typically presents as a unilocular or multilocular cyst within, or protruding from, the pancreas. Imaging studies
Epidermoid cyst in intrapancreatic accessory spleen
These are very rare lesions seen in younger adults (second to third decades). They occur almost exclusively in the tail of the pancreas where accessory spleens are not uncommon. Of note, accessory spleens are most frequently found at the perihilar region of the spleen (80% of cases) followed by the pancreatic tail.87
Similar to lymphoepithelial cyst, epidermoid cyst in intrapancreatic accessory spleen can also be misdiagnosed preoperatively as a cystic pancreatic neoplasm, such as intraductal
Squamoid cyst of pancreatic ducts
Squamoid cysts of pancreatic ducts are relatively small cysts, with a median size of 1.5 cm, and the vast majority of the cases are detected during workup for other conditions.92, 93 These cysts typically result from unilocular cystic dilatation of the ducts and have variable lining ranging from attenuated, flat, nonstratified squamous, to transitional, to mucosal-type stratified squamous epithelium (Fig. 12) as well as mucoproteinaceous acidophilic secretions within the lumen. The wall of the
Heterotopic pancreas
Heterotopic (ectopic) pancreatic tissue, independent from the vascular supply or anatomic connection to the pancreas, may occur from displacement of small amounts of pancreas during embryologic development.98, 99, 100 It is located most frequently in the stomach and proximal small intestine (Fig. 13), but can be identified in other organs, such as esophagus, gallbladder, hepatic or common bile ducts, spleen, and Meckel diverticulum.101, 102, 103
Depending on the size, location, and the
Pancreatic hamartoma
The term hamartoma refers to a focal overgrowth of cells and tissues native to the organ in which it occurs. Thus, hamartoma is regarded as a malformation rather than a true neoplasm.98, 115
Pancreatic hamartoma is rare, accounting for fewer than 1% of occurrences of tumorlike lesions.116 Usually presents as a well-demarcated, solid, or solid and cystic mass. It is often located in the head of the pancreas.117, 118, 119, 120, 121 Cases with multiple lesions have been reported.117, 118
Nesidioblastosis
Nesidioblastosis is a descriptor of the morphologic changes seen in functional disorders of the endocrine pancreas, characterized by persistent hyperinsulinemic hypoglycemia, due to defective non-neoplastic β-cells.2 It is usually seen in newborns30, 31 (also known as congenital hyperinsulinism127, 128); however, rare cases of adult nesidioblastosis do occur.98, 129, 130, 131, 132, 133
Nesidioblastosis can be diagnosed biochemically, usually within the first few weeks of life, through a series
Lipomatous pseudohypertrophy
Focal replacement of the exocrine pancreas with mature adipose tissue is common in the pancreas and usually correlates directly with body mass index.149, 150, 151 In contrast, lipomatous pseudohypertrophy is a distinct entity characterized by pseudotumor formation by adipose tissue, replacing almost an entire segment of exocrine parenchyma.152
Most common symptom at presentation is abdominal pain.152 In some cases, lipomatous pseudohypertrophy seems to be associated with specific syndromes such
Paraduodenal (groove) pancreatitis
Paraduodenal pancreatitis (also known as groove pancreatitis or cystic dystrophy of heterotopic pancreas) is a distinctive form of pancreatitis that occurs in the tissue between the duodenal wall and the pancreatic head. It often surrounds the minor ampulla and accessory duct.158, 159, 160
The vast majority of patients are young men with a history of alcohol abuse. The most common symptom is severe waxing and waning upper abdominal pain. Frequent clinical findings include stenosis of duodenum,
Summary
Benign neoplasms and tumorlike (pseudotumoral) lesions of the pancreas can be challenging, mostly due to lack of familiarity because of the lower number of cases, compared with malignant neoplasms, pathologists encounter on a daily basis.
Well-demarcated and spongelike appearance with innumerable small cysts of microcystic serous cystadenomas is so characteristic and usually does not create any diagnostic problems. In contrast, macrocytic serous cystadenomas can be difficult to diagnose, as the
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The authors have no conflict of interest to declare.