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This chapter gives a short and understandable overview of benign colon tumors. Benign tumors can be separated roughly into two major groups, namely, epithelial and mesenchymal lesions. These two groups can be separated in multiple subgroups that are explained in detail within the chapter.

Polyp is a well-known term mostly connected with tumours of the colon. A polyps can be defined as a small clump of cells that form on the lining of the colon. Polyps show a certain diversity and hence can be classified by aspect, origin (cell type), and malignant potency. Therapy and follow-up can be planned based on these aspects.

Standard and uniform tumor classification is essential for the optimal care of patients with cancer. Both surgical and medical oncologists are increasingly using tumor classification along with genetic mutational analysis for prognostic and predictive purposes. Organizations such as the American Joint Committee on Cancer, World Health Organization, and Union for International Cancer Control are responsible for creating a common language for tumor classification and cancer staging. Appropriate standardized terminology is beneficial to all clinical practitioners. National pathology organizations are increasingly mandating standardized reporting of all cancer resection specimens.

The two main inherited colorectal cancer syndromes are familial adenomatous polyposis (FAP) and Lynch syndrome (hereditary nonpolyposis colorectal cancer [HNPCC]), which account for less than 1 % and 3 % of colorectal cancers, respectively. FAP is characterized by the occurrence of multiple colorectal adenomas that often start to develop during the teenage years. A germ-line mutation in the APC gene located on chromosome 5 is found in about 85 % of patients with this phenotype. Without prophylactic surgery, nearly all will develop colorectal cancer. Surgery, including restorative proctocolectomy or total colectomy with ileorectal anastomosis, has greatly reduced the death rate from colorectal cancer, and now prognosis is dependent on desmoid tumors and duodenal polyposis.

HNPCC syndrome is more complex than FAP because more genes are involved, penetrance is less complete, and expression varies more. The recommendation is to try to determine the microsatellite instability (MSI) phenotype to test patients showing an MSI. Screening guidelines are well defined. Surgical management of HNPCC using segmental versus total colectomy is still debated.

A third syndrome, the MYH-associated polyposis syndrome, related to germ-line biallelic mutation of the human MUTYH gene, is an autosomal-recessive colon cancer syndrome. Other syndromes such as Peutz Jeghers syndrome, juvenile polyposis, and hyperplastic polyposis are seen less frequently.

Bowel cancer is the second most common cancer in Europe. The great majority of colon cancers are sporadic, and only 5 % are associated with a recognized familial pattern of inheritance. Complete flexible colonoscopy is the gold standard in the early detection of colorectal neoplasia. Patients present with alteration in bowel habit, frank rectal bleeding, or anemia. Symptoms such as intermittent abdominal pain, nausea, and vomiting are often secondary to partial obstruction or peritoneal dissemination.

Primary treatment for colon cancer is surgical resection of the primary and lymph nodes. Open and laparoscopic approaches are equally safe. Chemotherapy improves outcome but the prerequisite for adjuvant therapy is complete removal of the primary tumor. Neoadjuvant treatment is debated.

Rectal cancer should be managed by a multidisciplinary team (MDT) that includes input from gastroenterology, radiology, pathology, radiation oncology, and oncology in addition to colorectal surgery. The workup of suspected rectal cancer includes digital rectal examination, rectoscopy (proctoscopy), and biopsy. Staging of the tumor requires thoracic/abdominal computed tomography, pelvic magnetic resonance imaging, and complete colonoscopy to assess local tumor growth, systemic spread, and synchronous colonic lesions. The findings should be discussed during an MDT conference to determine the optimal sequence of treatment and the timing and extent of surgical resection. Radiotherapy, which is best delivered preoperatively, reduces the risk of local recurrence and may enhance survival in high-risk patients. Concomitant chemotherapy is used to increase the effect of radiotherapy (chemosensitizing radiation). Complete resection of the rectum en bloc with the surrounding mesorectal envelope enclosing draining lymphatic tissue, called total mesorectal excision, is the gold standard to decrease the risk of local recurrence and avoid injury to adjacent pelvic structures. Rectal cancers in the middle and upper third of the rectum can be treated with sphincter-saving anterior resection and colorectal anastomosis. Cancer in the lower third of the rectum may be amenable to low anterior resection with coloanal anastomosis or require abdominoperineal excision. Tumors involving the pelvic floor or external anal sphincter are treated with extralevator abdominoperineal excision and permanent colostomy. Preoperative chemoradiotherapy may result in complete clinical and radiological response. Such patients may enter a watch-and-wait program of intensive surveillance to detect tumor regrowth. Review of the surgical specimen pathology during a postoperative MDT meeting is important to ensure treatment quality and to determine the potential need for adjuvant chemotherapy. Follow-up after treatment, to detect metachronous colorectal cancer, local recurrence, or systemic disease, should continue for 5 years. Surgery and radiotherapy have adverse effects on function of the bowel, urinary bladder, sexual organs, and gonads, which warrant attention both at the onset of treatment and during follow-up.

Within the past few decades the incidence of anal cancer has increased worldwide, especially among the male homosexual population (men who have sex with men [MSM]), with an incidence up to 225 in 100,000. Human papillomavirus (HPV) infections are a main risk factor for the occurrence of anal cancer. The prevalence of anal HPV infection in human immunodeficiency virus (HIV)–negative MSM is 50–60 %, whereas the prevalence reaches almost 100 % in HIV-positive MSM. Anal intraepithelial neoplasia (AIN), which is associated with HPV, has been identified as a precursor lesion for anal cancer. Approximately 20 % of HIV-negative MSM are diagnosed with AIN, and high-grade epithelial neoplasia is already present in 5–10 %. The prevalence of high-grade AIN among HIV-positive MSM is considerably higher and can reach 50 %. In hypothetical models, screening examinations such as anal cytology and high-resolution anoscopy have been shown to be cost-effective and efficient in MSM. Based on these findings, regular anal screening tests should be recommended for at-risk patients. If anal cancer is diagnosed, positron emission tomography/computed tomography is recommended for staging. Radiochemotherapy is the standard treatment for most patients. Surgery is only advisable in patients with small tumors (<2 cm) of the anal margin or as a salvage procedure. Follow-up should be performed for 3 years and should include digital rectal examination and palpation of inguinal lymph nodes.

The majority of patients with pseudomyxoma peritonei of appendiceal origin who have complete cytoreductive surgery and hyperthermic intraperitoneal chemotherapy are cured. There is increasing evidence to support that similar principles of surgery and intraperitoneal chemotherapy can be effective in patients with peritoneal mesothelioma and colorectal peritoneal metastases. The key to a successful outcome is complete cytoreduction. This chapter discusses the evidence behind cytoreductive surgery and hyperthermic intraperitoneal chemotherapy, mainly in colorectal peritoneal metastases, and the challenges associated in selecting patients in whom this strategy is appropriate.

Retro rectal tumors (RRTs) in adults are rare. The incidence of these tumors was estimated at 1 in 40,000. The majority of these tumors are benign (80 %) and asymptomatic, and therefore are mostly discovered incidentally. However, given the risk of chronic pain, bleeding, infection, compression of adjacent organs (with digestive, urinary, obstetric, and/or neurological disorders), and especially the risk of malignant transformation, the current consensus is to perform systematic complete resection of any RRT. Nevertheless, only retrospective series with relatively few patients are reported, and recommendations for management and surgical approaches remain controversial.

Stomas have been an important tool in the treatment of many colorectal disorders for decades. However, the role of a stoma, certain characteristics of this procedure, and the possibilities of stoma care have changed over time. Without doubt, the formation of a stoma leads to a marked change in patients’ quality of life (QOL); preoperative marking of the stoma site, proper surgical technique, and professional care and counselling by a stoma therapist are important conditions necessary to achieving an acceptable QOL following this procedure. This chapter deals with the principles of surgical stoma formation (ileostomy, colostomy) the prevention and management of the most common complications of stoma surgery (e.g., prolapse, parastomal hernia, retraction)

Endoscopy, allowing real-time examination of the large bowel, has evolved into a major diagnostic and therapeutic modality in coloproctology. Diagnostic colonoscopy with or without biopsy is generally a very safe procedure (<1 % risk of complication). Polypectomy, stricture dilation, coagulation of angiodysplasia, and stent placement through malignant strictures are major therapeutic interventions that can be undertaken during colonoscopy. Therapeutic procedures may lead to occasional complications, but when performed by appropriately trained clinicians, the expected benefits outweigh complication risks in patients with a clear indication.

Colonoscopy has a major role in patients follow-up after endoscopic polypectomy or colorectal cancer resection because of the risk of developing further advanced neoplastic lesions in these patients, as outlined in recent European guidelines.

Chromoendoscopy, involving applications of tissue stains or dyes to the gastrointestinal mucosa, has been used for several years to improve the detection and characterization of neoplastic lesions. New endoscopic imaging technology has recently been developed, aiming to improve mucosal visualization, including improvements in image resolution, software processing, and optical filter technology.