There is a strong association between CD and small bowel cancer. The increased relative risk of small bowel cancer has been reported to be between 15.6 and 114.5 in comparison to the general population [26–30]. Cancer of the small intestine occurring in combination with CD is not as common as cancer of the large intestine. In addition, since cancer of the small intestine developing in patients with CD occurs in infected regions, it is very difficult to detect the disease at an early stage. This is because X-ray images of small intestinal cancer are similar to the images of strictures in patients with CD.

Making a definitive diagnosis of combined cancer was not possible before surgery, and the definitive diagnosis is obtained based on an intraoperative or postoperative pathological diagnosis. Palascak et al. reported that small bowel cancer was difficult to diagnose and was made preoperatively in only 1 of 20 patients who had CD as compared with 22 of 40 patients who had sporadic adenocarcinoma [31].

If we encounter such cases, we worry about whether to perform the reoperation or not, because the basic of surgery differs from CD and cancer.

Segmental resection is the performed surgical therapy for small bowel cancer in segmental CD. In patients with multiple small bowel strictures, concomitant strictureplasties should be performed in addition to the resection of the malignant stricture. Each stricture should be biopsied with frozen section evaluation to rule out the presence of synchronous cancers before a strictureplasty is carried out [32].

A male developed diarrhea and fever at the age of 18 years and was diagnosed with CD in a detailed investigation. He had poor compliance to the prescribed drug therapy and visited the hospital on an irregular schedule. At the age of 34, he was admitted to our hospital for close examination of repeated ileus symptoms that had begun about 4 months prior to treatment. As the ileus symptoms became aggravated, a long tube was inserted. Figure 7.4 shows findings obtained in a series of images of the small bowel, in which a lesion suggestive of internal fistula was noted near the terminal ileum.

Surgery was performed to remove the segment. During the laparotomy, multiple nodes were found in the peritoneal cavity and subjected to an intraoperative pathologic examination, which led to a diagnosis of peritoneal dissemination of a poorly differentiated adenocarcinoma. The lesion was surgically removed and an artificial anus was created on the opening side. The resected specimen is shown in Fig. 7.5. Cancer invasion was observed up to the serous surface and distention of the gut on the opening side. We determined that this was a case of poorly differentiated adenocarcinoma (Fig. 7.6).

Segmental resection is the performed surgical therapy for colonic cancer in segmental CD.

Subtotal colectomy is the procedure of choice in the presence of CD of the colon with malignant degeneration and sparing of the rectum. Following an abdominal colectomy, long-term surveillance with yearly endoscopy and biopsies of the remaining rectal segment is essential.

This procedure is generally performed for colonic cancer patients with pancolitis or with segmental colon and rectal disease or with colon and severe perianal disease.

It remains unresolved whether total proctocolectomy is required for colorectal cancer or dysplasia in CD as it is in UC or whether segmental resection might be adequate [33]. In CD, once dysplasia is identified, segmental resection is a more feasible option, especially if there has been a consistent lack of inflammation elsewhere in the intestinal tract [33]. In the patients with multifocal colonic dysplasia or rectal dysplasia, the need for an aggressive approach, namely, TPC, is easily justified. Moreover, in CD patients with severe perianal disease or incontinence, TPC with end ileostomy offers treatment of the anal disability not provided by lesser resections such as segmental colectomy or IRA. Most surgeons favor TPC when cancer or dysplasia is discovered in the colon, but this usually results in a permanent ileostomy. Both total colectomy with ileorectal anastomosis (IRA) and segmental colectomy in CD patients with comorbidities are possible alternatives but require careful preoperative patient counseling regarding cancer risk and compulsive postoperative surveillance of any remaining colorectum.

There has been a case of colonic high-grade dysplasia (HGD) reported in a patient with CD that recurred as metastatic cancer despite subtotal colectomy followed by annual colonoscopy surveillance with biopsy [34]. Therefore, to make a definitive recommendation about the management of colonic dysplasia in CD, a large study would be required.

Cancer of the internal or external fistula occurring in combination with CD is not as common as cancer of the large intestine. In addition, it is very difficult to detect the disease at an early stage. This is because X-ray images of fistula cancer are similar to the images of usual CD patients.

The association between cancer and fistula has long been recognized [35–38]. Unfortunately such cancers are often unresectable. However, it is possible on occasion to carry out a radical “en bloc” resection including the fistula.

An ileal bladder fistula was found at around the age of 40 years old in a male patient, and surgical treatment was recommended. However, it was left untreated, as no symptomatic aggravation occurred. After hematuria continued for 1 month, he visited the urology department at the age of 54. A cystoscopic examination found a tumor, which was diagnosed as mucinous cancer based on biopsy findings. Total pelvic exenteration was performed. A perioperative radiogram image and the excised specimen are shown in Fig. 7.8. The patient died of cancer at 8 months after the operation.