Rectal cancer developing from an anastomotic site 18 years after resection due to intussusception caused by Peutz-Jeghers polyposis in a 31-year-old man: a case report

Peutz-Jeghers syndrome (PJS) is an autosomal dominant disorder characterized by hamartomatous polyposis and mucocutaneous pigmentation [1]. Patients with PJS are at risk of developing malignant tumors in the gastrointestinal tract and/or other organs [2], although the mechanisms that lead to tumorigenesis in the gastrointestinal tract are unclear. The cumulative risk of colorectal cancer in patients with PJS between the ages of 15 and 64 years is 39%, and the relative risk is 84, resulting in an average age of 43 years in affected patients [2, 3]. Local recurrence after resection often occurs in malignant gastrointestinal cancers [4] but is rare in patients with benign tumors or other conditions, except in some cases of ulcerative colitis [5, 6]. Here, we report a case of rectal cancer in a young man with PJS that arose from the submucosal area of the anastomotic site of a prior high anterior resection of the rectum, which had been performed 18 years ago due to benign hamartomatous polyposis.

In the present case, an adenocarcinoma arose from the submucosal layer of the anastomotic site of a previous high anterior resection for polyposis caused by PJS polyposis in a young man, 18 years after surgery. The cancer arising from the submucosal area was identified by both endoscopic and histologic examinations. Two preoperative endoscopic examinations were performed. The first revealed a hemorrhagic tumor with a smooth surface and edge protruding from the surface of the rectum, which appeared through the orifice of the rectal mucosa. Curiously, the second examination 4 days later showed that the protruding tumor had disappeared, which is rarely observed in common rectal cancers. We hypothesize that the neck of the tumor at the rectal orifice may have been disrupted since the patient later informed us that he had excreted small hemorrhagic masses before the second examination. Histological examination revealed that the cancer mainly occupied the proper muscle layer and that granulation tissue covered the surface of the tumor but not the surrounding rectal mucosa; this indicated that a disruption had occurred at the neck of the tumor, as it was free from the surrounding rectal mucosa.

In addition, histological examination demonstrated that normal rectal mucosa was incorporated into the bone and surrounding stromal tissues, both of which the cancer had invaded into. This suggests that rectal mucosa in the bone or surrounding stromal tissues exists prior to bone formation or cancer development since normal rectal mucosa cannot naturally invade into these tissues.

We suggest that bone formation at the anastomotic site, or heterotopic ossification, is important for understanding this condition. In fact, although a few cases of ossification have been reported in Peutz-Jeghers polyposis or colorectal cancer, ossification in the gastrointestinal tract is extremely rare [7, 8]. Since heterotopic ossification commonly occurs as a complication of trauma [9], the process of wound healing after traumatic injury at the anastomotic region may have induced heterotopic ossification, as well as the incorporation of rectal mucosa into the bone and surrounding stromal tissues in our patient. We had knowledge of the patient’s clinical history of long hospitalization after high anterior resection, in addition to the findings from the second low anterior resection of strong adhesion between the anastomotic region and the surrounding intestines. Together, these clinical and histological data imply that traumatic injury such as anastomotic leakage may have occurred in this region (Fig. 4). An alternative explanation is that the cavity, a so-called dog ear formation, which results from traditional double stapling anastomosis, was formed due to the original surgical procedure; however, the lack of clinical and surgical records makes it difficult to precisely ascertain its origins.

Although there is a high risk of colorectal cancer in patients with PJS, cancer developing at an anastomotic site has never been reported. In cases of common colorectal cancer, local recurrence at the anastomotic site after surgery often occurs within 3 years, but rarely after 5 years [4, 10]. However, in the present case, the initial tumors were not malignant but benign hamartomatous polyps, which were completely resected. Therefore, it is possible that the cancer in this case arose independently of the initial Peutz-Jeghers polyposis. On the other hand, given the high risk of colorectal cancer in patients with PJS, it is possible that the cavity at the anastomotic site was covered with rectal mucosa with malignant potential [3]. Chronic persistent inflammation may have occurred within the cavity which, in addition to the cavity being in an enclosed environment, may have led to cancer development. This is similar to what occurs in inflammatory bowel diseases such as ulcerative colitis that secondarily develop into colorectal cancer [11]. Thus, we concluded that the patient with PJS may have developed cancer in the rectal mucosa with malignant potential that was located in the submucosal cavity or had been incorporated into the bone or stromal tissues. We hypothesize that this was further stimulated by chronic persistent inflammation during the 18-year period after the initial high anterior resection of the rectum due to Peutz-Jeghers polyposis.