Benign Neoplasms of the Small Intestine Clinical Presentation

Clinically, benign small-bowel lesions are characterized by a lack of identifying symptoms. A review of published reports reveals that multiple findings can occur sporadically; no hallmark presentation has been described. Possible signs and symptoms are as follows ^{[2, 3, 4]} :

• Abdominal pain - This is generally nonspecific, dull, and epigastric in location; pain is more commonly associated with larger lesions, which may cause symptoms of intermittent bowel obstruction
• Constipation
• Melena
• Perforation
• Nausea
• Diarrhea
• Gastrointestinal (GI) hemorrhage
• Volvulus
• Vomiting
• Palpable mass
• Obstruction
• Anorexia
• Early satiety
• Anemia
• Intussusception

The interval from symptom onset to diagnosis has been reported to range from less than 1 month to more than 1 year, with a mean symptom duration of 6 months. Despite their frequently unobtrusive nature, benign small-bowel tumors may manifest primarily as secondary complications of their growth. The following may be noted:

• Bowel obstruction - This is associated with as many as 30% of benign small-bowel tumors, and these tumors remain the leading cause of intussusception in adults
• Volvulus - Volvulus from serosal ependymal lesions has also been reported
• GI bleeding - This is a more frequent occurrence, occurring in as many as 38% of lesions in one series; blood loss may be occult, detected only as heme-positive stool, or it may be acute and copious, as with larger vascular lesions; such bleeding may ultimately require transfusion, embolization, and/or emergency surgery
• Perforation - Free perforation of small-bowel tumors into the peritoneal cavity, with resultant development of peritonitis and requirement for emergency laparotomy, has also been documented

Benign small-bowel tumors may develop as a single lesion or as multiple lesions of several subtypes. The types of tumors include the following:

• Hyperplastic polyps
• Adenomas
• GI stromal tumors (GISTs)
• Lipomas
• Hemangiomas
• Peutz-Jeghers syndrome

Hyperplastic polyps

Hyperplastic polyps are benign mucosal growths frequently observed in the duodenum and proximal ileum. Frequently discovered upon routine upper endoscopy, the polyps may be single or multiple. They are generally asymptomatic with no malignant potential and may be removed endoscopically with biopsy forceps or an Endosnare.

Adenomas

Three types of small-bowel adenomas have been described, as follows:

• Adenomatous polyps
• Brunner gland adenomas ^[10]
• Villous adenomas

In general, they may develop as single or multiple lesions, both sessile and pedunculated. Histologically, they appear as intraluminal extensions of the mucous membrane and submucosal architecture with multiple acini supported on a central fibrovascular core. Varying degrees of differentiation are encountered across and within tumors. ^[11]

Complications of continued growth include obstruction, bleeding, intussusception, and, occasionally, malignant degeneration, particularly with larger villous lesions. ^[12] Specifically, Brunner gland adenomas develop most often along the posterior wall of the duodenum at the junction of the first and second portions. Focal, multifocal, or diffuse, they exhibit benign proliferation of the Brunner glands with scattered ductal and stromal elements.

Villous adenomas, though exceedingly rare, have most frequently been described in the duodenum. ^[13] Bleeding and obstruction are their most common complications, though, like their counterparts in the colon and stomach, they may be associated with malignant degeneration. Villous adenomas larger than 4 cm are at particular risk for malignant elements. ^[13]

Gastrointestinal stromal tumors

In several reports, GISTs (formerly known as leiomyomas and leiomyosarcomas) are the most common symptomatic small-bowel lesions. They have been found in all areas of the small bowel, including within the Meckel diverticulum. Featuring nests of spindle-shaped cells located between the muscularis propria and the muscularis mucosa, these intramural lesions may form intraluminal masses, extraluminal masses, or transmural (dumbbell-shaped) lesions. ^[14]

Histologic features of smooth muscle may or may not be seen with light microscopy; however, this finding has not yet been assigned any prognostic value. ^{[15, 16]} Both focal lesions and anular lesions have been described, often with features of surface ulceration or deeper necrosis. Such degeneration may lead to bleeding and marked hemorrhage, which are the most common complications observed with this family of tumors. Minor bleeding from surface erosion may occur because the tumors are continually buffeted and bathed by intestinal contents. Brisk arterial bleeding may result from necrosis involving tumor arterioles occurring deep within the lesion.

Other complications of GISTs include bowel obstruction, intussusception, tumor perforation, and potential malignant degeneration. In general, size is the defining characteristic for complications from GISTs. The larger the tumor, the more likely it is to obstruct or twist within the bowel lumen. Similarly, larger tumors are more likely to outgrow their blood supply, necrose, bleed, and degenerate.

Differentiating between benign and malignant GISTs can be difficult. In several published reviews, benign smooth-muscle tumors are generally two to three times more common than the sarcoma variants. Current diagnostic criteria for pathologic examination of malignancy include the following:

• Tumor cell size
• Degree of cellular differentiation
• Number of mitotic figures per high-power field (hpf)

A finding of more than two mitotic figures per 10 hpf is generally considered worrisome for malignancy. ^[17]

Lipomas

Small-bowel lipomas are benign submucosal tumors of mesenchymal origin. These tumors are often located in the ileum and may frequently develop as pedunculated or submucosal lesions. They may be sessile or ependymal and may grow undetected to a size sufficient to produce symptoms of colicky abdominal pain and intermittent bowel obstruction. ^[18] Intussusception has also been reported.

Histologic features include collections of mature adipose tissue and fibrous tissue strands. Evidence of surface ulceration, central necrosis, and hemorrhage may be present. Collections of adipose tissue may be found near the ileocecal valve. These deposits may clinically mimic other lesions, both radiographically and endoscopically.

Hemangiomas

Hemangiomas of the small bowel are rare vascular tumors of three types, as follows ^{[19, 20]} :

• Capillary
• Cavernous (the most common type)
• Mixed

Hemangiomas may be solitary or multiple and may account for up to 10% of small-bowel lesions. ^[21]

GI bleeding is a frequent complication. The blood loss may be chronic (resulting in longstanding occult anemia) or profound (necessitating massive transfusions, emergency laparotomy, or both for control of acute hemorrhage). ^[22]  Additional uncommon complications include small-bowel obstruction, intussusception, intramural hematoma, and perforation. With light microscopy, hemangiomas appear as blood-filled sinusoidal spaces intermingled with varying amounts of connective tissue. Occasionally, the lesions contain smooth muscle cells.

Diagnosis and localization of symptomatic lesions remain a challenge. Preoperative arteriography or intraoperative maneuvers, such as transillumination of the bowel or intraoperative ultrasonography (US), may be employed to increase localization success.

Case reports have documented the successful use of capsule endoscopy to aid in the diagnosis of these often difficult-to-detect lesions. ^{[23, 24]}

Peutz-Jeghers syndrome

Peutz-Jeghers syndrome is an autosomal dominant disorder featuring mucocutaneous pigmentation (eg, on the face, lips, and buccal mucosa) and benign GI hamartomas. ^{[7, 25]}  These polyps may be found in the small bowel in as many as 90% of affected individuals. The stomach and the colon are frequently involved, and tumors outside the GI tract are also described.

The hereditary defect is associated with mutation on the LKB1 gene (19p2,3). ^[26]  Histologically, the lesions feature a distinctive frondlike appearance with a stromal/smooth muscle core covered by acinar glands and normal mucosa. Nuclear atypia is absent.

Secondary complications are common and are often related to the significant numbers of hamartomas present within the bowel. Colicky abdominal pain, GI bleeding, and obstruction (frequently the result of intussusception) are widely described. ^[27]

Malignant transformation is reported, and other non-GI cancers may be found concomitantly.

Current surveillance recommendations for the small-bowel lesions include biannual barium upper GI series and flexible endoscopy beginning at age 10 years. ^[28]

The physical examination is usually unrevealing, except in the case of larger tumors (>6 cm), which occasionally manifest as a palpable abdominal mass. Abdominal pain may occasionally be elicited upon palpation of the lesion. Most patients exhibit no distinct physical findings upon examination.