Nonepithelial tumors of the colon and rectum are rare and represent fewer than 1% of all neoplasms of the colon and the rectum. They can be categorized as benign or malignant. In this chapter we will briefly discuss benign lymphoid hyperplasia, lipomas, and leiomyomas, as well as leiomyosarcoma and the primary lymphomas of the colon and rectum. A large portion of the chapter will address cavernous hemangiomas of the colon and rectum. Neurofibromas and rhabdomyosarcomas are extremely rare lesions; only nine cases of rhabdomyosarcoma have been recorded in the world literature. Endometriosis and the neuroendocrine tumors are discussed in other chapters in this text.
Benign Nonadenomatous Lesions of the Colon and Rectum
Benign Lymphoid Hyperplasia
A benign lymphoid polyp is an aggregation of lymphoid tissue with a covering of normal mucosa. These lesions are most common in the rectum and the distal sigmoid, where they can be single or multiple, broad based, or have a short pedicle. They are homogeneous in appearance and are usually pale. These lesions are usually small—2 to 4 mm in diameter—but sometimes mucosa-associated lymphoid tissue can measure several centimeters. Lymphoid hyperplasia is more prominent in children and young adults, in whom the polyps are numerous and can mimic polyposis. In daily practice, lymphoid polyps are removed during colonoscopy because they are difficult to differentiate from small adenomas or serrated polyps. This is especially the case when polyp detection rate is an important quality indicator for colonoscopy. Usually, the pathologist makes the diagnosis. Benign lymphoid polyps need no follow-up and carry no risk.
Although lipomas are the second most common neoplasm of the colon after adenomas, they are uncommon, with an incidence of less than 1%. Gender distribution is equal, and the average age at diagnosis is 62.4 years. Lipomas are submucosal lesions ranging in size from 0.5 mm to larger than 6.5 cm. They can be pedunculated or sessile and are most often found in the right colon, followed by the transverse colon, sigmoid colon, and rectum. Although most lipomas are asymptomatic and are found incidentally, they can cause intermittent bowel obstruction (if the lipoma is near the ileocecal valve), colocolonic intussusception, or prolapse through the rectum.
The typical endoscopic appearance of a submucosal lipoma is a yellowish, smooth polyp with a broad base or a short, thick stalk. The mucosal pit pattern is endoscopically normal, although the submucosal position of the lipoma causes stretching of the mucosa, allowing the endoscopist to see the normal blood vessels. The “pillow sign” is the classic endoscopic diagnostic maneuver. Biopsy forceps push on the center of the presumed lipoma, which indents and then gradually regains its shape, much like a pillow does when it is poked. A superficial biopsy of a lipoma yields only normal mucosa. However, when a diathermy snare is used to remove overlying mucosa, fat protrudes from this site. An important differential, especially in right-sided lipomas, is a carcinoid tumor. This tumor also looks yellow, but in contrast to lipomas, it is hard and fixed, with no “pillow sign.”
Treatment of lipomas of the colon and rectum is dictated by the clinical presentation. Most asymptomatic lipomas are not treated, but their existence and position are noted. Treatment of a symptomatic lipoma depends on its presentation and position. Once the diagnosis has been made, the lipoma can be removed with a diathermy snare en toto or in a piecemeal fashion. An innovative technique for excision of larger lipomas of the colon and rectum has been described. The diathermy snare is placed around the lipoma, and the snare is gradually tightened. This maneuver ruptures the lipoma through the mucosa, thus allowing visualization and easier excision of the lesion. Only an experienced colonoscopist should attempt this technique and piecemeal excision of larger lipomas. Because of their high fat content, lipomas resist conduction of electricity more than do adenomas. More current is required for snaring, and the risk of perforation is greater. Most lipomas should be left alone.
Patients presenting with intussusception, obstruction, or bleeding from a lipoma require surgery after stabilization and resuscitation. When colonic obstruction is present or when a lipoma is ulcerated with inconclusive results of biopsies, then the lesion should be considered malignant and resected with oncologic technique.
Phillips first described hematochezia from an intestinal hemangioma in 1839, and to this date only about 300 cases have been recorded in the literature. The rectosigmoid is the most common site of cavernous hemangioma of the gastrointestinal tract. In about 80% of cases the patient presents with anemia and recurrent, painless, bright red rectal bleeding. A life-threatening gastrointestinal hemorrhage is rare but may require an emergency abdominoperineal resection ( Table 65-1 ). A high index of suspicion is required for the surgeon to make the correct diagnosis.
|Sex||Age, yr||Location||Operation||Follow-up, yr|
|Male||63||Rectosigmoid||Abdominoperineal resection||Postoperative mortality|
Hemangiomas of the gastrointestinal tract are classified as multiple phlebectasias, capillary hemangiomas, and cavernous hemangiomas. Most are cavernous, in which there are large, thin-walled vascular channels without true encapsulation, and typically with more smooth muscle fibers than capillary lesions. The pathogenesis of cavernous hemangiomas is a dynamic process of budding from ectopic mucosal implants of mesodermal tissue. This process of budding infiltration explains the transmural and mesenteric involvement of these lesions. Cases of local infiltration into the uterus, urinary bladder, and sacrum have been reported. Figure 65-1 shows a rectal cavernous hemangioma invading the perirectal fat in a 3-year-old boy, illustrating thickening of the rectal wall and mesorectum and invasion into the pelvic wall. Three years after resection he presented with a recurrence of the lesion involving not only the right buttock but the spinal canal near the cauda equina. He had a tender, right ischiorectal mass and associated anemia. Clinically, the mass measured 8 cm × 5 cm × 5 cm, was hard, and felt like a “bag of marbles.” A computed tomographic (CT) scan revealed a recurrent cavernous hemangioma of the ischiorectal fossa, pelvic wall, and sacrum ( Fig. 65-2 ). Selective angiography was performed and indicated internal iliac origin and spinal cord plexus origin. A magnetic resonance image of the spinal cord indicated that the cauda equina was involved ( Fig. 65-3 ). A multidisciplinary team including an interventional radiologist, pediatric neurosurgeon, and colorectal surgeon decided not to embolize or surgically approach this lesion because the child had minimal symptoms. We also believed that arterial embolization was too dangerous because of the vessels of origin. Part of the lesion, involving the ischiorectal fossa, had spontaneously thrombosed, and this patient still has no abnormal neurologic findings. This young man is now 22 years old and living a normal life. He still has the same persistent yet asymptomatic recurrence of the cavernous hemangioma involving the ischiorectal fossa, the bladder, and the feeding vessel from the spinal cord. A recent review showed that the radiographic appearances have not changed.