Elsevier

Surgical Pathology Clinics

Volume 9, Issue 4, December 2016, Pages 619-641
Surgical Pathology Clinics

Benign Tumors and Tumorlike Lesions of the Pancreas

https://doi.org/10.1016/j.path.2016.05.007Get rights and content

Abstract

The pancreas is a complex organ that may give rise to large number of neoplasms and non-neoplastic lesions. This article focuses on benign neoplasms, such as serous neoplasms, and tumorlike (pseudotumoral) lesions that may be mistaken for neoplasm not only by clinicians and radiologists, but also by pathologists. The family of pancreatic pseudotumors, by a loosely defined conception of that term, includes a variety of lesions including heterotopia, hamartoma, and lipomatous pseudohypertrophy. Autoimmune pancreatitis and paraduodenal (“groove”) pancreatitis may also lead to pseudotumor formation. Knowledge of these entities will help in making an accurate diagnosis.

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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